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https://en.wikipedia.org/wiki/Sodium_triphosphate
Sodium triphosphate
 | |
| Names | |
|---|---|
| IUPAC name Pentasodium triphosphate | |
| Other names sodium tripolyphosphate, polygon, STPP | |
| Identifiers | |
| ECHA InfoCard | 100.028.944  |
| E number | E451 (thickeners, ...) |
PubChem CID | |
| RTECS number |
|
| UNII | |
CompTox Dashboard (EPA) | |
| Properties | |
| Na5P3O10 | |
| Molar mass | 367.864 g/mol |
| Appearance | white powder |
| Density | 2.52 g/cm3 |
| Melting point | 622 °C (1,152 °F; 895 K) |
| 14.5 g/100 mL (25 °C) | |
| Hazards | |
| Safety data sheet | ICSC 1469 |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Related compounds | |
Other anions | Trisodium phosphate Tetrasodium pyrophosphate Sodium hexametaphosphate |
Other cations | Pentapotassium triphosphate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
 verify (what is   ?) | |
| Infobox references | |
Sodium triphosphate (STP), also sodium tripolyphosphate (STPP), or tripolyphosphate (TPP),[1]) is an inorganic compound with formula Na5P3O10. It is the sodium salt of the polyphosphate penta-anion, which is the conjugate base of triphosphoric acid. It is produced on a large scale as a component of many domestic and industrial products, especially detergents. Environmental problems associated with eutrophication are attributed to its widespread use.[2]
Preparation and properties[edit]
Sodium tripolyphosphate is produced by heating a stoichiometric mixture of disodium phosphate, Na2HPO4, and monosodium phosphate, NaH2PO4, under carefully controlled conditions.[2]
- 2 Na2HPO4 + NaH2PO4 → Na5P3O10 + 2 H2O
In this way, approximately 2 million tons are produced annually.[3]
STPP is a colourless salt, which exists both in anhydrous form and as the hexahydrate. The anion can be described as the pentanionic chain [O3POP(O)2OPO3]5−.[4][5] Many related di-, tri-, and polyphosphates are known including the cyclic triphosphate P3O93−. It binds strongly to metal cations as both a bidentate and tridentate chelating agent.
Uses[edit]
In detergents[edit]
The majority of STPP is consumed as a component of commercial detergents. It serves as a "builder," industrial jargon for a water softener. In hard water (water that contains high concentrations of Mg2+ and Ca2+), detergents are deactivated. Being a highly charged chelating agent, TPP5− binds to dications tightly and prevents them from interfering with the sulfonate detergent.[3]
Food applications[edit]
STPP is a preservative for seafood, meats, poultry, and animal feeds.[3] It is common in food production as E number E451. In foods, STPP is used as an emulsifier and to retain moisture. Many governments regulate the quantities allowed in foods, as it can substantially increase the sale weight of seafood in particular. The United States Food and Drug Administration lists STPP as "generally recognized as safe."[citation needed]
Other uses[edit]
Other uses (hundreds of thousands of tons/year) include ceramics (decrease the viscosity of glazes up to a certain limit), leather tanning (as masking agent and synthetic tanning agent - SYNTAN), anticaking agents, setting retarders, flame retardants, paper, anticorrosion pigments, textiles, rubber manufacture, fermentation, antifreeze."[3] TPP is used as a polyanion crosslinker in polysaccharide based drug delivery.[6] Toothpaste.[7][8][9][10][11][12][13]
Health effects[edit]
High serum phosphate concentration has been identified as a predictor of cardiovascular events and mortality. Whilst phosphate is present in the body and food in organic forms, inorganic forms of phosphate such as sodium triphosphate are readily adsorbed and can result in elevated phosphate levels in serum.[14] Salts of polyphosphate anions are moderately irritating to skin and mucous membranes because they are mildly alkaline.[1]
Biopolymers
E.Ann MacGregor, in Encyclopedia of Physical Science and Technology (Third Edition), 2003
II.C.1 Structure
The monomers from which nucleic acids are made are more complex than those of either proteins or polysaccharides. These are nucleoside triphosphates and they can be considered to consist of three parts (Fig. 17)—a triphosphate group, a five-carbon sugar in the furanose ring form, and a cyclic base—that is a ring system with basic properties (which can associate with H+ in water). Five different bases are commonly found in nucleic acids.
FIGURE 17. Common nucleoside triphosphates from which nucleic acids are made. The numbering system for the carbon atoms of the sugar rings and the initial letters commonly used as abbreviations for the base names are shown.
In DNA the sugar is 2-deoxy-D-ribose. In RNA the sugar is D-ribose. From this difference came the names of the two polymers. The common bases are adenine, guanine, cytosine, thymine, and uracil; adenine and guanine are purines, while the others are pyrimidines. In each type of nucleic acid, DNA or RNA, only four bases occur commonly—in DNA these are guanine, adenine, cytosine, and thymine and in RNA they are guanine, adenine, cytosine, and uracil. Each base becomes attached to a sugar through a β-glycosidic link. Such a combination of sugar plus base is a nucleoside. The triphosphate is linked to carbon 5′ of the sugar; nucleoside phosphates such as shown in Fig. 17 are also known as nucleotides.
During nucleic acid synthesis monomers are joined together with elimination of a pyrophosphate (diphosphate) grouping as shown in Fig. 18a. From two nucleotides, a dinucleotide is formed and the new link, a phosphodiester link, connects carbon 3′ of one nucleotide sugar to carbon 5′ of the next. A third nucleotide can become joined at carbon 3′ of the right-hand sugar ring, and the process can continue to give a chain of several linked nucleotides—an oligonucleotide—or a chain of hundreds or even thousands of covalently bonded nucleotides, a polynucleotide (Fig. 18b). Most DNA molecules consist of two polynucleotide chains, while RNA molecules usually contain only one polynucleotide chain.
FIGURE 18. (a) Formation of a dinucleotide. (b) The chain structure of a polynucleotide or nucleic acid. X = H in DNA and OH in RNA; Y is often a triphosphate group.
At one end of a chain the group attached to carbon 5′ of the sugar ring is not involved in a phosphodiester link. This is referred to as the 5′ end of the chain and by convention is written at the left end of the chain. At the other end, the grouping on carbon 3′ of the sugar is not involved in a phosphodiester linkage; this is the 3′ end of the chain and is written on the right (Fig. 18b).
Nucleic acids differ from one another in the lengths of the polynucleotide chains of their molecules and in the sequence of bases along these chains. For any one nucleic acid, however, all the molecules are identical in size and base sequence. Any sequence of bases is possible in a nucleic acid. Abbreviations are often used to represent nucleic acid structure, and the simplest of these involves giving the base sequence of a chain in terms of the initial letters of the base names, starting from the 5′ end of the chain; in this convention sugar and phosphate groups are not mentioned. Thus if, in Fig. 18b, Base 1 = guanine, Base 2 = thymine, Base 3 = adenine, and Base n = cytosine, the structure would be represented as GTA … C.
The two polynucleotide chains in DNA molecules are believed to be wound around each other to give a regular secondary structure, a right-handed double helix (Fig. 19). The two chains run in opposite directions with the phosphate and sugar groups on the outside of the helix and the bases in the interior. The proposal for this structure was first made by Watson and Crick and led to their being awarded the Nobel Prize in 1962. Since the bases are flat, they can stack on top of one another in any sequence almost at right angles to the helix axis. The two chains of the helix are held together by hydrophobic associations between the stacked bases and also by specific hydrogen bonding between pairs of bases, where one base of a pair is contributed by each chain. In an unstrained structure there are 10 base pairs per complete turn of the helix. The two chains of the helix are always approximately the same distance apart (the helix has a diameter of 20 Å) and so the base pair must always consist of one double-ring base, a purine (A or G), hydrogen bonded to a single-ring base, a pyrimidine (T or C). This base-pairing is specific; adenine on one chain always bonds to thymine on another, while guanine on one chain bonds to cytosine on the other. The result is that the sequence of bases on one chain determines the sequence on the second chain, if base-pairing is to take place. For example, if the base sequence of a chain segment is … ACTAGTC … then in the second chain T must bond to A, G to C, etc., and the double helix would have the sequence
FIGURE 19. The double helix of DNA.
The sequences of the two chains are said to be complementary to each other. The helices are not completely regular along their length, but small variations in helix architecture occur with variations in base sequence. These relatively minor changes are important for DNA-protein recognition.
The DNA molecules may be several thousand to over a million nucleotides long, and some segments of the base sequence code for protein structure, while others form control elements. Yet other sequences code for the structures of the r-RNA and t-RNA essential for protein synthesis. The long DNA molecules behave as flexible rods that can coil up if long enough, and in some bacteria the two ends of a molecule can join together to give a closed loop. There is some evidence that, for GC sequences, a stretch of left-handed double helix can form. The importance of this secondary structure of DNA, called Z-DNA, in biological systems is not yet clear.
Except for a few viral ribonucleic acids, all RNA molecules are single-stranded. The polynucleotide chains can fold up on themselves, and if base sequences of two stretches of a chain are complementary, a stretch of right-handed double helix, similar to a DNA double helix, can form. In an RNA double helix, there are approximately eleven base pairs per turn of the helix, and uracil, instead of the thymine of DNA, base-pairs with adenine. The single polynucleotide chains are folded to give short stretches of double helix separated by single-stranded nonhelical segments.
The secondary structures (helices) and tertiary structures (overall chain folding) of RNA are not uniform and differ with the type of RNA. The chain folding is often complex, involving short helices, loops, and even 3- or 4-way junctions of single-stranded chain. Messenger RNA molecules carry in their base sequences the information specifying protein amino acid sequence. There is one messenger for each protein, and so m-RNA molecules vary greatly in length and sequence; hence they differ in secondary and tertiary structure. Ribosomal ribonucleic acids form part of the structures known as ribosomes, where protein synthesis takes place in a living cell. In simple bacteria, each ribosome contains three sizes of r-RNA, designated 5 s, 16 s, and 23 s RNA. (The numbers 5 s, 16 s, and 23 s relate to the speed of movement of the RNA molecules through a solution spinning in a high speed centrifuge, and depend on the size of the RNA molecules). These molecules are typically 120, 1500, and 2900 nucleotides long, respectively. The base sequences of many r-RNAs are known, and segments of complementary base sequence have been observed, so that double helix formation is believed to occur within the ribosome. Transfer RNAs, which bring the amino acids to the sites of protein synthesis, are the smallest ribonucleic acids, being on average about 80 nucleotides long. The base sequences of many t-RNAs have been studied and it has been found that they contain many “unusual” bases, (i.e., bases other than A, G, U, and C). For example, thymine, a “normal” constituent of DNA, is found in t-RNA. All the t-RNAs examined so far have segments of complementary base sequence which can make up four short segments of double helix. Each t-RNA is specific for one amino acid, and so many t-RNAs exist, differing in the number and sequence of nucleotides. Despite this, it is believed all t-RNA molecules have approximately the same overall chain folding (i.e., tertiary structure) shown inFig. 20. Unusual base pairs (e.g., G–U pairs) are found in this structure as well as base triplets (i.e., three bases held together by hydrogen bonding).
FIGURE 20. Tertiary structure of a t-RNA. The four short double helical segments are shown shaded. [Adapted with permission from Rich, A., and RajBhandary, U. L. (1976) Annu. Rev. Biochem. 45, 805–860. Copyright 1976 Annual Reviews Inc.]
Inorganic Substances in Biochemical Applications
James E. House, Kathleen A. House, in Descriptive Inorganic Chemistry (Third Edition), 2016
23.2.1 Production of Energy by ATP
Energy is produced in cells by a series of complex reactions that depend on biological catalysts known as enzymes. In some living systems, the energy production involves a cycle that is dependent on a complex material known as adenosine triphosphate or ATP, which functions as a coenzyme. A coenzyme is a substance that is necessary for the enzyme to serve as a catalyst for a biochemical reaction. ATP consists of a triphosphate chain that is similar to that contained in the “polyphosphoric” acids described in Section 14.8.2. Attached to the triphosphate group is the ribose sugar and attached to the sugar moiety is an adenosine ring. The structure of ATP is usually shown in the anion form with the hydrogen ions removed from the phosphate groups as shown in Figure 23.6.
Figure 23.6. The structure of the adenosine triphosphate anion.
A highly charged ion such as the ATP anion (or any highly charges species such as Fe3+, , or N3−) is not normally stable in aqueous solutions. However, with the presence of multiple oxygen atoms having unshared pairs of electrons and negative charges, that portion of the ATP molecule is a good chelating agent and it binds to Mg2+ ions, which stabilizes the ATP in anion form. Even though this occurs, the terminal phosphate can be removed in an energetically favorable step. This occurs because of the energy of interaction of the liberated phosphate ion with the solvent (H2O) and the greater stability of the chelate with Mg2+ ions. If the Mg2+ ion is solvated by several water molecules, forming a chelate with the triphosphate group is favorable because of the chelate (entropy) effect as water molecules are displaced (see Section 20.4.2).
In Chapter 6, it was shown that in an acid molecule the number of oxygen atoms with no hydrogen attached affects the strength of the acid as a result of resonance. In the ATP molecule, the electrons around bridging oxygen atoms are localized to a greater extent than are those of oxygen atoms in terminal positions on the phosphate groups. Thus, there is some contribution to the favorable energy of hydrolysis as a result of increased resonance stabilization of the products compared to the ATP molecule.
The product that results when a phosphate group is removed from ATP is known as adenosine diphosphate or ADP. Thus there is an equilibrium that can be shown as
However, the ATP ion has a −4 charge and the phosphate ion produced is the anion of a weak acid. Therefore, hydrolysis occurs so that the phosphate liberated can be present as HPO42− or H2PO4−, and the reactions producing these species from are energetically favorable. As a result, the reaction illustrated in Eq. (23.5) releases 30.5 kJ/mol.
Single-Electron Elementary Steps in Homogeneous Organometallic Catalysis
Nicolaas P. van Leest, ... Bas de Bruin, in Advances in Organometallic Chemistry, 2018
1.3.2 Coenzyme B12-Dependent Enzymes
Coenzyme B12, also known as vitamin B12 or 5′-deoxyadenosylcobalamin, is a cobalt–corrin complex which is the cofactor of a variety of enzymes catalyzing three types of reactions: (i) intramolecular rearrangements, (ii) methylations (e.g., in the synthesis of methionine), and (iii) reduction of ribonucleotides to deoxyribonucleotides.13 Coenzyme B12 comprises a cobalt–carbon bond and is hence a rare example of an organometallic biomolecule containing a metal–alkyl moiety. The Co
C bond is formed by an unusual nucleophilic attack of cobalamin's cobalt on the 5′-methylene carbon of adenosine triphosphate (ATP), thereby replacing the triphosphate group to form 5′-deoxyadenosylcobalamin (Scheme 6).13
Scheme 6. Formation of coenzyme B12 (5′-deoxyadenosylcobalamin) from cobalamin and adenosine triphosphate (ATP).
The low bond-dissociation energy (BDE) of the CoC5′ bond, estimated to be only 31.5 kcal mol− 1,14 holds the key to the ability of the coenzyme to serve as a reversible radical reservoir. Substrate binding induces further destabilization of the CoC bond and causes it to be homolytically split, thereby creating a 5′-deoxyadenosyl radical () which plays a crucial role in the consequent catalytic cycle. As an example, Scheme 7A shows the catalytic cycle of coenzyme B12-dependent isomerases, which catalyze 1,2-rearrangements involving the interchange of a hydrogen atom of one carbon with the substituent (e.g., OH, NH2, or an alkyl group) from an adjacent carbon.15 The cycle starts with HAT from a substrate CH bond to the 5′-deoxyadenosyl radical. The thus formed substrate-centered radical then undergoes the 1,2-migration, followed by a second HAT from 5′-deoxyadenosine (dAdo–CH3) to the product radical. As an example, Scheme 7B shows the catalytic cycle of glutamate mutase-catalyzed 1,2-migration of an sp3-hybridized glycyl radical.15
Scheme 7. (A) General catalytic cycle of coenzyme B12-dependent isomerases. The corrin ligand is depicted schematically for simplicity. “dAdo” represents the 5′-adenosyl group. (B) Glutamate mutase-catalyzed 1,2-migration of an sp3-hybridized glycyl radical.
Amino Acids, Peptides and Proteins
Jonathan L. Huot, ... Daniel Kern, in Comprehensive Natural Products II, 2010
5.14.4.1.3(ii) The 3D structure of T. thermophilus AsnRS bound to the small ligands
Crystals of the enzyme bound to asparaginyl-adenylate (Asn∼AMP) diffracting at 3.2 Å of resolution were obtained by cocrystallization of the protein with ATP and MgCl2. The structure was refined from crystals formed by the protein bound to the nonhydrolyzable 5′-O-(N-asparaginyl-sulfamoyl) adenosine analogue diffracting at 2.65 Å.141
Interactions between the subunits intimately link the dimer interface with the ATP-binding site. The adenine ring and the γ-phosphate of ATP interact, as in other class II aaRSs, with conserved residues from motifs 2 and 3. Three Mg2+ ions associate with the triphosphate group, one with the α- and β-phosphates and with Asp352 and Glu361 and the other two with the β-and γ-phosphates on each side of the phosphoester bond. These interactions stabilize ATP in the bent conformation, which is essential for the activation of the aa by class II aaRSs. The adenosine moiety interacts as in ATP: the adenine ring with residues Glu210, Leu218, Phe235, and Arg412 and the 2′ OH ribose with Ile362 and Gly409. Glu361 interacts with the 3′ OH and together with Asp352 through a Mg2+ ion with the O− of the phosphoryl group. Arg208 interacts with the oxygen of both the phosphoryl and the aa carbonyl groups. The aa α-amino group is positioned by Glu164, Ser185, and Gln187, whereas the carbonyl and the amido groups of the side chain make hydrogen bonds with Arg368 and Glu225, respectively.
Comparison of the 3D structures of free and Asn∼AMP-complexed AsnRSs shows that activation of Asn promotes domain movements in the protein and an increased ordering of the loops surrounding the catalytic site resulting in a more precise delimitation of the catalytic site. The motif 2 loop moves in a concerted way with the C-terminal peptide toward the active site, closing its access and sequestering the activated Asn. These contacts promote rotation by 2.5 Å of the N-terminal β-barrel relative to the catalytic domain. The novel conformation is stabilized by intersubunit interactions. Exposure of motif 2 loop on the enzyme surface agrees with cleavage by limited proteolysis of a peptide of Mr 26 kDa starting with the His243 included in this loop.140 Involvement of this loop in the stabilization of the complex formed with the small ligands is supported by the temperature-dependent increase in Km for Asn and ATP of the E. coli HO202 AsnRS mutant in which Pro231 from motif 2 is substituted by Leu without significant alteration of the kcat,136 suggesting that this residue is involved in positioning of the loop and in sequestration of the small ligands in the catalytic site.
Polymers in Biology and Medicine
D.M. Perrin, in Polymer Science: A Comprehensive Reference, 2012
9.02.17 Nucleobase-Modified Aptamers
The development of aptamers against protein targets continues to provide many exciting applications for diagnostics, imaging, and even the development of a clinically used drug (Macugen). Nevertheless, many protein targets that were recognized with high affinity fell into two categories: highly basic proteins (e.g., thrombin) and nucleotide/RNA-binding proteins (e.g., reverse transcriptase). Similarly, small molecules that were readily recognized by aptamers were either hydrophobic (intercalators), cations (metals or cations such as arginine), or nucleotides (e.g., ATP), which presented H-bonding and base-pairing interactions that would be readily recognized by the limited chemical repertoire of unmodified aptamers. Besides the use of 2′-fluoro/amino modifications, which have largely been chosen to confer properties of nuclease resistance, the development of functionalized aptamers has been slowly forthcoming and not without mixed results. As noted, the use of 5-(1-pentynyl)-dUTP enabled the selection of thrombin-binding aptamers; however, the Kd was substantially increased compared to the unmodified aptamers, which suggested that in this particular case, modifications did not improve affinity.213 In addition, as early as 1999, selection for ATP-binding aptamers with the cationic 5-(3-aminopropargyl)-UTP resulted in aptamers with a modest threefold higher affinity over those selected with UTP that lacked the cationic group.214 Interestingly, the modified aptamer had a nearly identical sequence to that of the previously reported unmodified sequence, which did not recognize the triphosphate group to any significant extent. This coincidence of sequence homology suggested that the preponderant mode of small molecule recognition by aptamers, even modified ones, was still largely governed by folds that were modification independent. Subsequently, use of aminopropyl-UTP provided for ATP-binding aptamers of different sequence, which indeed recognized the triphosphate portion of ATP in addition to the nucleobase, and which were modification dependent.215 More recently, cation-modified aptamers have been generated against sialyllactose216 and glutamate.136 Recent success with modified dNTPs in the selection of aptamers against two target proteins was recently described in quantitative terms by Vaught et al.,217 who showed that target proteins, which were found to be somewhat refractory to selection using unmodified dNTPs, could be recognized by aptamers with substantially increased affinity that were generated using various dUTP analogs containing hydrophobic groups shown in Figure 23.
Figure 23. Various dUTP analogs used by Vaught et al. to select for high-affinity aptamers against proteins that could not be targeted with the same affinity when TTP was used instead in an unmodified selection.
In summary, as with modified DNAzymes, where in certain cases selection with modified dNTPs greatly enhanced the catalytic properties of catalysts under certain conditions, the use of modified dNTPs to improve aptamer affinity will likely show slowly improving results as a greater number of selections is undertaken given the recent availability of a greater number of modified dNTPs that have been reported. It is likely, however, that improvements will be seen on an ad hoc basis as it remains to be determined which conditions and targets for which modifications will result in high affinity of the selected aptamers. Nevertheless, as shown in the case of the Mg2+-independent RNA-cleaving DNAzymes, neither robust catalytic activity nor modification-dependent activity necessarily results from selecting with dNTPs that have been chosen for optimal incorporation rates. More work will be needed to see if the similar results are seen with modified aptamers. Nevertheless, while sequence space coverage may not be the only factor in terms of selecting robust activity with modified dNTPs, certainly any successful selection that resulted from otherwise poorly incorporated dNTPs would further benefit from polymerases with enhanced tolerance to increase sequence space coverage. Indeed, in order to enhance sequence space coverage, ultimately new polymerases will be needed. Towards this end, the evolution of DNA polymerases reflects a different and exciting, yet complementary, approach that will ultimately be essential for realizing the full potential for selecting with modified dNTPs. Thus, the final section of this chapter briefly describes progress toward understanding the polymerases needed for nucleic acid selection.
Polymers for Advanced Functional Materials
D. Khodagholy, ... R.M. Owens, in Polymer Science: A Comprehensive Reference, 2012
8.05.3.2.1 Polymers as recognition elements
The main application of polyfluorenes in sensor applications so far has been for amplification of optical signals. The primary mechanisms are either by fluorescence resonance energy transfer (FRET) or by photoinduced charge transfer (PCT), although finding out which mechanism is involved is often complicated. For polyfluorenes, their photoluminescent spectra are very compatible with fluorophores used in the realm of bioassays such as fluorescein and Texas red, and their use has been demonstrated in a variety of assay types including protein assays, DNA-binding assays, and antioxidant-sensing assays. A key paper in 2002 showed the detection of an antibody–antigen complex as follows: a fluorescence quencher in complex with an antigen forms a weak bond with the water-soluble conjugated polymer in aqueous solution. Upon addition of the specific antibody, the quencher antigen binds to the antibody and the conjugated polymer is unquenched resulting in a photoluminescent signal.137
A further example of optical sensing with water-soluble conjugated polymers was by Li et al., who reported a water-soluble polythiophene derivative that displays colorimetric and fluorescent responses to adenosine triphosphate (ATP) and its analogues in a dose-dependent manner. The authors hypothesize that this is due to electrostatic and hydrophobic cooperative interactions.138 The authors carried out experiments on related compounds such as adenosine diphosphate and found that the effect was most pronounced with ATP, leading them to hypothesize that the color change was as a result of interaction between the negative charges of the triphosphate group combined with a synergistic effect from the hydrophobic adenine. Combined, these interactions serve to shift the π–π* transition to longer wavelengths, leading to a color change from yellow to red, as shown in Figure 35.
Figure 35. Changes in the color of solutions of a poly(3-alkoxy-4-methylthiophene) derivative induced by the addition of equimolar amounts of various anions.
Reproduced with permission from Li, C.; Numata, M.; et al. Angew. Chem., Int. Ed. 2005, 44 (39), 6371–6374.138Spontaneous complexation between CPEs and DNA has previously been described and has been used as the basis for many nucleotide-based sensors. A DNA sensor has been shown using peptide nucleic acid (PNA), labeled with a fluorophore.139 In the presence of the polyfluorene, the PNA, which has no net charge, forms a complex with its complementary single-stranded DNA, thus allowing efficient transfer of fluorescence resonance energy from the polymer to the fluorophore. This principle is shown in Figure 36. In the presence of a nonspecific or noncomplementary DNA strand, the DNA forms an electrostatic interaction with the polyfluorene, but the distance from the PNA is too large to allow FRET. Several variations on this theme allowing detection of RNA, double-stranded DNA, single-nucleotide polymorphisms, and DNA microarrays have been described and are summarized by Bazan and Wang,140 all involving either quenching of existing fluorescence or generation of fluorescence upon binding of a target to its partner.
Figure 36. Schematic representation for the use of a water-soluble conjugated polymer with a specific PNA-C* optical reporter probe to detect a complementary ssDNA sequence.
Reproduced with permission from Gaylord, B. S.; Heeger, A. J.; et al. Proc. Natl. Acad. Sci. U.S.A. 2002, 99 (17), 10954–10957.139Modified polyfluorenes have also been used to detect glucose via peroxide production, a mechanism which could be extended to other redox enzymes. He et al. show the use of the cationic conjugated polymer, poly(9,9-bis(6′-N,N,N-trimethylammonium-hexyl)fluorine phenylene) (PFP-NMe3+) and peroxyfluor-1 with boronate protecting groups (Fl-BB) for optical detection of H2O2.141 In the absence of H2O2, the lack of electrostatic interactions between the above molecules means that they remain separate, and therefore, no quenching occurs. However, in the presence of H2O2, the anionic quencher, fluorescein, is formed. This system showed detection between 15 and 600 nM H2O2. The system was therefore used for detection of glucose, in approximately the same concentration range, as shown in Figure 37.
Figure 37. Calibration curve corresponding to fluorescence quenching caused by the addition of glucose.
Reproduced with permission from He, F.; Tang, Y. L.; et al. Adv. Funct. Mater. 2006, 16 (1), 91–94.141Another type of polyelectrolyte-based fluorescent sensor is based on anionic polymers such as BpPPESO3, whose structure is shown in Figure 38(a). These are polyelectrolytes that contain a fluorescent tag present either as part of a single large conjugated system or as part of an array that exhibits distinct fluorescence from the monomer. The latter type can either have a chromophore covalently linked to the polymer backbone or be associated electrostatically via charge. Again, these molecules are water soluble and may easily be absorbed onto oppositely charged supports. A review of these compounds and sensors based on their use has been published by Ogawa et al.142 As before, the general sensing mechanism relies on quenching of a fluorescent signal by a binding event between a ligand and a receptor, or dequenching of a fluorescent signal upon addition of a receptor to a complex formed between a polymer and a ligand. Many variations on this theme have been described and these assays have been reported to be particularly amenable to use within a microwell plate reader format and therefore suitable for high-throughput screening.142 These compounds have, for example, been used successfully to measure protease activity with enzymes such as phospholipases. In this study, BpPPESO3 (an anionic polyphenylethylene-type CPE, structure shown in Figure 38(a)) forms a complex with a lipid substrate of phospholipase C, resulting in the formation of a fluorescent complex. Upon hydrolysis of the substrate to diacylglycerol and the phosphoryl base, the fluorescence dissipates, as shown in Figure 38(b). This assay functions at low concentrations of substrate (nanomolar–micromolar) and enzyme (nanomolar), with good specificity.
Figure 38. (a) Structures of the materials used and the reaction scheme for hydrolysis of 10CPC by PLC and (b) the mechanism of PLC turnoff assay. 1,2-didecanoyl-sn-glycerol (DAG); 1,2-didecanoyl-sn-glycero-3-phosphocholine (10CPC); phospholipase C (PLC).
Reproduced with permission from Liu, Y.; Ogawa, K.; Schanze, K. S. Anal. Chem. 2008, 80 (1), 150–158.12Faid and Leclerc reported the use of biochromic modified polythiophenes, functionalized with biotin, which upon binding of avidin to the polythiophene underwent a chromic shift (from yellow to violet), which could be measured by absorbance spectroscopy.143,144
Charych et al. reported a direct colorimetric assay for the detection of influenza virus, using a polydiacetylene bilayer immobilized on a glass microscope slide and functionalized with sialic acid (the virus receptor molecule). Upon binding of the virus, a color change is visible to the naked eye, but could also be quantified by absorption spectroscopy. The authors demonstrated by physical characterization that the packing of the bilayer with bound virus was different from that without virus, resulting in a change of the optical properties of the polymer backbone.145
- the breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy; destructive metabolism.
https://sciencing.com/usage-sodium-tripolyphosphate-6499754.html
What Is the Usage of Sodium Tripolyphosphate?
Sodium tripolyphosphate, also known as pentasodium triphosphate, pentasodium tripolyphosphate or sodium triphosphate, is used in a wide range of applications in the manufacture of cleaning products and food preservatives as well as in water treatment facilities.
Manufacture
Sodium tripolyphosphate is a sodium salt of triphosphoric acid. It is manufactured in chemical laboratories by mixing disodium phosphate and monosodium phosphate.
A Powerful Cleaning Agent
Sodium tripolyphosphate is used in a variety of cleaning products. It improves the ability of various ingredients in the detergent to penetrate the fibers of clothes (as well as other surfaces and materials to be cleaned) more deeply, and aids in foaming and bubbling. Therefore, most chemical plants that make sodium tripolyphosphate list "detergents" as the primary area of use for this chemical.
Food Additive
Sodium tripolyphosphate also gives a fresh appearance to meat and seafood while slowing down spoilage. The chemical helps to preserve the natural color of meat and fish and improves their texture. This is done by improving the water-holding capacity of animal products and consequently slowing down their drying
Tanning Agent for Leather
Sodium tripolyphosphate is listed as a tanning agent for leather. Interestingly, the chemical is also used as an oil contamination resistance agent in paper production. So, it can both help manufacturers apply the right color to a medium as well as keep unwanted color away.
Other Uses
Other uses of sodium tripolyphosphate include petroleum refining, metallurgy, mine applications and water treatment. The last application is made possible by its pH buffering ability, meaning that it can "soften" acidic water by neutralizing its acidity. This quality is one of the reasons it is added to detergents.
Citric Acid Powder Uses
A common food, pharmaceutical and cleaning product additive, citric acid is a weak, water-soluble organic acid naturally found in many citrus fruits, such as lemons and limes. It was first discovered by the 8th century Arabic chemist Abu Musa Jabir ibn Hayyan (also known as Geben), but not purified to its current form until the 18th century.
Food Production
Citric acid powder is commonly added to both carbonated and non-carbonated soft drinks as a flavoring agent, adding a tart taste to the beverage, and as a preservative due to its anti-microbial properties. It is added to candy to add a tart flavor, but also to stabilize the sugars and enhance texture (citric acid helps give candies a gel-like consistency). Citric acid is used in the production of jams and jellies to help control the food's pH level, assisting in its consistency and shelf life. It can also be found in processed cheese to stabilize and emulsify the oil and water content of the cheese and keep it from separating.
Pharmaceutical Applications
Citric acid powder can add flavor to medicine preparations, masking the taste of the chemical components. It is also added as an emulsifier, keeping ingredients in liquid preparations from separating. The most common use of citric acid powder in is in combinations with bicarbonates to create an effervescent, fizzing effect.
Household and Industrial Uses
Citric acid powder is added to many detergent products, such as laundry soap and shampoo, as well as industrial strength products, to maintain an alkaline pH, which helps the surfactants--cleansers--work more effectively. The citric acid powder is easy to rinse away with the cleanser, as it is both water soluble and biodegradable.
https://sciencing.com/usage-sodium-tripolyphosphate-6499754.html
What Is the Usage of Sodium Tripolyphosphate?
Sodium tripolyphosphate, also known as pentasodium triphosphate, pentasodium tripolyphosphate or sodium triphosphate, is used in a wide range of applications in the manufacture of cleaning products and food preservatives as well as in water treatment facilities.
Manufacture
Sodium tripolyphosphate is a sodium salt of triphosphoric acid. It is manufactured in chemical laboratories by mixing disodium phosphate and monosodium phosphate.
A Powerful Cleaning Agent
Sodium tripolyphosphate is used in a variety of cleaning products. It improves the ability of various ingredients in the detergent to penetrate the fibers of clothes (as well as other surfaces and materials to be cleaned) more deeply, and aids in foaming and bubbling. Therefore, most chemical plants that make sodium tripolyphosphate list "detergents" as the primary area of use for this chemical.
Food Additive
Sodium tripolyphosphate also gives a fresh appearance to meat and seafood while slowing down spoilage. The chemical helps to preserve the natural color of meat and fish and improves their texture. This is done by improving the water-holding capacity of animal products and consequently slowing down their drying
Tanning Agent for Leather
Sodium tripolyphosphate is listed as a tanning agent for leather. Interestingly, the chemical is also used as an oil contamination resistance agent in paper production. So, it can both help manufacturers apply the right color to a medium as well as keep unwanted color away.
Other Uses
Other uses of sodium tripolyphosphate include petroleum refining, metallurgy, mine applications and water treatment. The last application is made possible by its pH buffering ability, meaning that it can "soften" acidic water by neutralizing its acidity. This quality is one of the reasons it is added to detergents.
I read that when baking soda and lime juice are combined, sodium salts are created. Could this type of salt be considered a triphosphate?
No. First off, there's almost no phosphate in lime juice so there's no way to produce triphosphate (assuming that you mean trisodium phosphate) from lime juice. Second, bicarbonate doesn't have a high enough pH to convert any phosphate to the trisodium phosphate form. You would need to add sodium hydroxide to do this. Since lime juice contains considerable citric acid, you will make, among other things, trisodium citrate. But lime juice contains many organic acids, not just citric acid so in reality you would be preparing a mixture of sodium salts of organic acids including citric acid.
https://theintercept.com/2020/05/26/coronavirus-gileand-remdesivir-treatment/
DESPITE THE HYPE, GILEAD’S REMDESIVIR WILL DO NOTHING TO END THE CORONAVIRUS PANDEMIC
A combination of generic drugs appears to be more effective in fighting the coronavirus than Gilead Sciences’ remdesivir.
GILEAD SCIENCES’ REMDESIVIR has been heralded as our best hope in fighting the coronavirus pandemic. Unfortunately, the antiviral drug doesn’t seem of much help to patients with Covid-19, the disease caused by the coronavirus. And while the company’s clever rollout has generated excitement among investors, politicians, and the public, a combination of generic drugs that appears to be more effective in fighting the coronavirus has flown under the radar.
Desperation for the limited supply of remdesivir is so great that Virginia will hold a lottery to determine which of the almost 1,500 severely ill patients in the state will be able to get its several hundred donated doses of the drug. In Minnesota, state officials have come up with an action plan to allocate their supply of the Covid-19 treatment, which calls for designating “triage officers” who will randomly choose among equally eligible patients. And in Alabama, physicians on a coronavirus task force set up by the governor will determine which patients get remdesivir.
Some hospitals there will receive just a single course of treatment. Still, Alabama’s state health officer, Dr. Scott Harris, recently offered his thanks to Gilead, the drug’s manufacturer, which donated some 940,000 vials of the drug to the federal government that are being distributed by state health departments. “Although the total supply of remdesivir is limited, we are grateful that hospitalized COVID-19 patients with severe disease in Alabama can receive this potentially lifesaving medication,” said Harris.
Read Our Complete CoverageThe Coronavirus CrisisIt is amid these feelings of scarcity and indebtedness that Gilead is setting the price for its antiviral medicine. The company, which has already arranged for distribution of remdesivir in 127 countries, is expected to begin selling it commercially as soon as June. And while a 10-day course of the drug, which was developed as a potential Ebola treatment with at least $79 million in U.S. government funding, costs only about $10 to produce, according to an estimate by the Institute for Clinical and Economic Review, its market price is expected to be several hundred times that amount.
Still, price gouging isn’t what has many scientists upset about remdesivir. It’s the fact that the coronavirus drug that has boosted hopes and sent Gilead’s stock price (and according to some analysts, the entire stock market) soaring doesn’t seem to do much for coronavirus patients.
“Remdesivir doesn’t work at all, as far as I can tell, or has only a minor effect,” said William Haseltine, a scientist who has spent decades studying viruses and helped lead the U.S. government response to the HIV/AIDS epidemic. “It is comparable to Tamiflu and maybe not even as good,” Haseltine added, referring to another antiviral drug that has been available by prescription for 20 years and is expected to be sold over the counter in the coming months.
Haseltine, who founded the divisions of biochemical pharmacology and human retrovirology at Harvard University’s School of Public Health, pointed out that Gilead hasn’t released data showing remdesivir’s effect on viral load in people with Covid-19. Meanwhile, the only available information on how the drug affects the amount of the coronavirus in patients, a Chinese study of the drug published in The Lancet, showed that the drug did not lower the viral load.
“That’s why I call it the fuzzy-wuzzy drug,” said Haseltine. “When the Chinese tried to find the antiviral effect, it wasn’t there.”
Instead, the excitement about remdesivir is based largely on a study sponsored by the National Institute of Allergy and Infectious Diseases that showed people taking the drug had a faster recovery than those who didn’t take it: 11 days on average compared to 15 for those taking a placebo. An article published on May 22 in the New England Journal of Medicine showed mild improvement in hospitalized patients that took remdesivir, though the drug didn’t appear to be of any help to the sickest patients, who needed to receive high-flow oxygen through ventilators or other means. Nor did the drug significantly improve a patient’s chance of surviving Covid-19.
Nevertheless, at an April 29 Oval Office press conference with President Donald Trump, NIAID Director Dr. Anthony Fauci declared that preliminary results from that trial proved that “a drug can block this virus.” Since then, remdesivir has been positioned as our savior and Gilead as its benevolent dispenser.
While some patients and their families have spent the past few weeks frantically trying to procure remdesivir, another Covid-19 treatment has been quietly been shown to be more effective. Although neither option appears to be the much-needed cure for Covid-19, a three-drug regimen offered a greater reduction in the time it took patients to recover than remdesivir did. People who took the combination of interferon beta-1b, lopinavir-ritonavir, and ribavirin got better in seven days as opposed to 12 days for those who didn’t take it. Critically, the treatment has another leg up on Gilead’s: It clearly reduced the amount of the coronavirus in patients who took it, according to a study published in The Lancet on May 8.
Yet so far there has been no stampede of patients demanding the new regimen or lotteries to mete out the doses, which may be due at least in part to the fact that the treatment hasn’t been the subject of a major marketing campaign. It’s worth noting that each of the three drugs in the new combination is generic, or no longer under patent, which means that no company stands to profit significantly from its use.
In contrast, Gilead, a company that had more than $22 billion of revenue in 2019 and stands to make money from remdesivir for many years, has been carefully orchestrating the rollout of its new treatment, doling out small, tailored bits of encouraging information to the press and highlighting its compassionate use program.
It’s not unusual for pharmaceutical companies to paint their products in a rosy light or go to questionable lengths to maximize profit. And Gilead, which secured a lucrative orphan drug status for remdesivir in March before reversing course two days later, has faced widespread criticism before — particularly for the exorbitant pricing of its HIV medicine Truvada and hepatitis C drug sofosbuvir, which sells for $1,000 a pill.
But during the pandemic, buzz, politics, and greed are playing an even greater role than usual in determining which drugs are widely used while the usual scientific process for evaluating their safety and effectiveness is being sped up and curtailed. Trump, who whipped up excitement about the malaria drug hydroxychloroquine, a drug he has taken himself despite not having Covid-19, has led the way.
“You have a president putting intense pressure on companies, regulators, and others in an effort to salvage his reelection,” said Dr. Michael Carome, director of health research at Public Citizen. The consequences, Carome warmed, could be deadly. “My great worry is that with all this hype and the press from the White House, that we’ll bring something to market much too quickly and harm a lot of people. That’s the danger.”
Already, the risk of death has been shown to be elevated in Covid-19 patients who take hydroxychloroquine. According to a study published in The Lancet last week, the approximately 15,000 people who received hydroxychloroquine or the closely related drug chloroquine were roughly twice as likely to die as those who didn’t take them.
The benefits of all drugs have to be balanced against their harms. In the case of remdesivir, those dangers appear to include possible damage to the kidney and liver. While the risks and benefits are typically clarified with further study, the NIAID called off the remdesivir trial that might have offered more information about both so that the patients who were getting the placebo could take the drug.
In addition to possibly hurting patients, basing decisions about coronavirus therapies and vaccines on hype rather than science also carries the risk of prematurely investing in one product at the expense of another. “It’s possible that we’re now investing a lot of effort in pursuing a drug that could lead to less research being done on something that could have been safer or more effective,” Carome said about what he described as questionable enthusiasm for remdesivir. After the drug received Emergency Use Authorization from the Food and Drug Administration on May 1, Public Citizen submitted a FOIA request for the complete data underlying the decision. The FDA has not provided the group with any documents and usually treats such data as proprietary.
Meanwhile, the excitement around another coronavirus development seems to be moving faster than the science. Last week, the biotech company Moderna also moved markets with a vague announcement about the preliminary results of a study. In this case, the company described initial findings of a trial of its potential coronavirus vaccine as “triumphant,” though they were based on eight people from a relatively early stage of research.
“Most products that pass this phase ultimately fail,” said Public Citizen’s Carome. While the company summarized its data, it didn’t release it. “We need to see the details, but we probably won’t.”
Share Your Coronavirus StoryClick here to learn about contacting a reporter securely, or email us at coronavirus@theintercept.comThe vaccine development process promises to get faster and more vulnerable to conflicts of interest. On May 14, Trump announced Operation Warp Speed, the administration’s effort to produce and distribute a coronavirus vaccine by the end of the year, despite experts’ insistence that the process will likely take years. The operation is being led by former pharmaceutical executive Moncef Slaoui, who has received more than $13.5 million from pharmaceutical and biotech firms since 2016. Slaoui was also holding 155,000 shares of Moderna, whose value increased by more than $2 million after the good news about its vaccine hit the airwaves. In an unusual arrangement, the compensation for his government work is only $1 and is exempt from the usual federal disclosure and conflict-of-interest laws. After Sen. Elizabeth Warren called attention to his conflict of interest, Slaoui divested his shares in Moderna and announced that he would donate to cancer research the money he made off their increase after he joined Operation Warp Speed.
While vaccination may be the best hope to bring an end to the pandemic as quickly as possible, mistakes made because of haste or conflicts of interest could be devastating. Because the plan is to vaccinate some 1 billion people worldwide, even infrequent side effects could manifest on a huge scale. The wrong vaccines could even spread disease. “They could give you a nasty cold that you could give to unvaccinated people,” said Haseltine.
The current power of politics and greed over science make such outcomes more likely. “I fear that the warp speed group will distort our regulatory process and that the administration will put its thumb on the scale to favor an outcome regardless of the cost to human life,” said Haseltine. “People think warp means very fast, but warp also means distorting.”
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