scholarly journals ON PHOSPHOTUNGSTIC ACID STAINING. II

1971 ◽  
Vol 19 (11) ◽  
pp. 648-653 ◽  
Author(s):  
G. QUINTARELLI ◽  
J. A. CIFONELLI ◽  
R. ZITO
Keyword(s):  
Amino Acids ◽  
Phosphotungstic Acid ◽  
Hydroxyl Groups ◽  
Amino Groups ◽  
Ionic Interaction ◽  
Neutral Sugars ◽  
Acidic Conditions ◽  
Heparin Oligosaccharides ◽  
Positively Charged ◽  
Acid Glycosaminoglycans

Phosphotungstic acid (PTA) used at different concentrations in water was combined with various compounds (amino acids, proteins, acid glycosaminoglycans, glycoproteins and simple sugars). The results obtained indicated that PTA interacts with positively charged groups, that the sugar-hydroxyls do not take part in the interaction and that the type of binding involves electrostatic forces. To substantiate these findings further, heparin and heparin oligosaccharides were N-desulfated, combined with PTA and the precipitates were analyzed. It was found that the interaction had taken place only between the metal and the desulfated hexosamine amino groups and that when the N-desulfated product was acetylated no PTA binding occurred. When PTA was used at higher concentrations and in extremely acidic conditions, a precipitation of proteins, amino acids, acid glycosaminoglycans and neutral sugars ensued. This complex formation was interpreted as due to ionic interaction between the polyacid and the protonated hydroxyl groups.

Measurement of proteolysis in cheese: relationship between phosphotungstic acid-soluble N fraction by Kjeldahl and 2,4,6- trinitrobenzenesulphonic acid-reactive groups in water-soluble N

1994 ◽  
Vol 61 (3) ◽  
pp. 437-440 ◽  
Author(s):  
Yvette Bouton ◽  
Remy Grappin
Keyword(s):  
Amino Acids ◽  
Free Amino Acids ◽  
Free Amino ◽  
Phosphotungstic Acid ◽  
Water Soluble ◽  
Hydroxyl Groups ◽  
Amino Groups ◽  
Reactive Groups ◽  
Primary Amino

Free amino groups produced during cheese ripening are used to indicate the extent of cheese proteolysis. Several studies have shown a high correlation between the level of free amino acids and the flavour of Gouda (Aston et al. 1983) or Comté (Grappin & Berdagué, 1989). Measurement of the level of free amino acids seems useful for the investigation of flavour chemistry in cheese (Lemieux et al. 1990). The determination of N fractions is often used to estimate the degree of proteolysis in cheese, but since this procedure is laborious and time consuming several attempts have been made to replace it by more rapid methods (Ardö & Meisel, 1991). Since its introduction by Satake et al. (1960), the 2,4,6-trinitrobenzenesulphonic acid (TNBS) method has been widely used for the determination of free amino groups. Because TNBS does not react with the imino groups of histidine and proline or the hydroxyl groups of tyrosine, serine or threonine, it has been accepted as a selective reagent for primary amino groups (Burger, 1974). Measurement of N by Kjeldahl in the phosphotungstic acid (PTA)–sulphuric acid extract (Gripon et al. 1975) estimates the N of free amino acids and low molecular mass peptides. The purpose of this study was to compare the TNBS and PTA-soluble N methods in order to find out whether the TNBS procedure can replace that of PTA-soluble N in the determination of a cheese proteolysis index.

Frameworks of Transition Metals and Linkers with Two or More Functional Groups

2000 ◽  
Vol 658 ◽  
Author(s):  
Slavi C. Sevov
Keyword(s):  
Amino Acids ◽  
Transition Metals ◽  
Functional Groups ◽  
Organic Molecules ◽  
Layered Structures ◽  
Amino Groups ◽  
Effect Of Ph ◽  
Open Framework ◽  
Acidic Conditions ◽  
New Compounds

ABSTRACTHybrid inorganic/organic materials with open-framework or layered structures are known for many transition metals linked by functionalized organic molecules such as organic diphosphonates, polycarboxylates, polynitriles, etc., species with more than one equivalent functional groups. We have studied the effect of pH on such a system of cobaltmethylenediphosphonate and report three new compounds, Na3Co[(O3PCH2PO3)(OH)],Na2Co(O3PCH2PO3)•H2O, and Co2[(O3PCH2PO3)(H2O)], that form at very basic, moderately basic, and acidic conditions, respectively. More interestingstructural chemistry should be expected from linkers with two or more different functionalities. Both the carboxylic and phosphonic groups in carboxyethylphosphonic acid are used to coordinate to cobalt or calcium atoms in the new compounds Co3(O3PCH2CH2COO)2•6H2O and Ca(O3PCH2CH2COOH)•H2O. Taking one more step further in complexity we have also studied linkers with three different functional groups, phosphonated amino acids. The structures of two new compounds, Zn(O3PCH2CH(NH3)COO) and Zn(O3PCH2CH2CH(NH3)COO), are threedimensional frameworks made of zinccoordinated by both the carboxylic and phosphonic ends of the organic molecules. The amino groups are protonated and terminal in the voids of the frameworks.

scholarly journals ON PHOSPHOTUNGSTIC ACID STAINING. I

1971 ◽  
Vol 19 (11) ◽  
pp. 641-647 ◽  
Author(s):  
G. QUINTARELLI ◽  
R. ZITO ◽  
J. A. CIFONELLI
Keyword(s):  
Heavy Metal ◽  
Sialic Acid ◽  
Chondroitin Sulfate ◽  
Phosphotungstic Acid ◽  
Model Systems ◽  
Organic Cations ◽  
Hydroxyl Groups ◽  
Sublingual Gland ◽  
Ph Dependent ◽  
Positively Charged

In this study histochemical experiments have been carried out in order to understand the "staining mechanism" of phosphotungstic acid (PTA). One of the main objectives of this project was to investigate the mode of interaction of the heavy metal and to define the type of functional groups in the substrates responsible for PTA binding. Therefore, tissues containing known macromolecules were selected and utilized as model systems. Epiphyseal cartilage, rat sublingual glands, human bone and purified collagen were used to study the interaction of the polyacid with chondroitin sulfate (cartilage), sialic acid (sublingual gland) and collagen (purified collagen and bone). The results obtained suggested that PTA does not interact with chondroitin sulfate, with sialic acid or with the hydroxyl groups of the sugar moieties of these macromolecules. Rather, the binding appeared to be selective for positively charged groups. Since PTA interaction to organic cations was pH-dependent, it is suggested that the heavy metal binds by means of coulombic forces and that no hydrogen bonds are involved.

A new method of quaternizing amines and its use in amino acid and peptide chemistry

1976 ◽  
Vol 54 (20) ◽  
pp. 3310-3311 ◽  
Author(s):  
Francis C. M. Chen ◽  
N. Leo Benoiton
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Methyl Iodide ◽  
New Method ◽  
Hydroxyl Groups ◽  
Amino Groups ◽  
Small Peptides ◽  
Peptide Chemistry ◽  
Selective Reagent ◽  
Derivatives Of

Methyl iodide and potassium bicarbonate in methanol is presented as a mild, efficient, and selective reagent for the quaternization of amino groups. It does not attack hydroxyl groups. Its use with amino acids, derivatives of lysine, and small peptides is described.

scholarly journals Hydroxyapatite formation on graphene oxide modified with amino acids: arginine versus glutamic acid

2016 ◽  
Vol 13 (114) ◽  
pp. 20150986 ◽  
Author(s):  
M. Tavafoghi ◽  
N. Brodusch ◽  
R. Gauvin ◽  
M. Cerruti
Keyword(s):  
Amino Acids ◽  
Graphene Oxide ◽  
Amino Groups ◽  
Phosphorylated Proteins ◽  
Charged Amino Acids ◽  
Simulated Body Fluids ◽  
The Individual ◽  
Local Supersaturation ◽  
Positively Charged ◽  
Hydroxyapatite Formation

Hydroxyapatite (HA, Ca 5 (PO 4 ) 3 OH) is the main inorganic component of hard tissues, such as bone and dentine. HA nucleation involves a set of negatively charged phosphorylated proteins known as non-collagenous proteins (NCPs). These proteins attract Ca 2+ and PO 4 3− ions and increase the local supersaturation to a level required for HA precipitation. Polar and charged amino acids (AAs) are highly expressed in NCPs, and seem to be responsible for the mineralizing effect of NCPs; however, the individual effect of these AAs on HA mineralization is still unclear. In this work, we investigate the effect of a negatively charged (Glu) and positively charged (Arg) AA bound to carboxylated graphene oxide (CGO) on HA mineralization in simulated body fluids (SBF). Our results show that Arg induces HA precipitation faster and in larger amounts than Glu. We attribute this to the higher stability of the complexes formed between Arg and Ca 2+ and PO 4 3− ions, and also to the fact that Arg exposes both carboxyl and amino groups on the surface. These can electrostatically attract both Ca 2+ and PO 4 3− ions, thus increasing local supersaturation more than Glu, which exposes carboxyl groups only.

scholarly journals Anchoring Water Soluble Phosphotungstic Acid by Hybrid Fillers to Construct Three-Dimensional Proton Transport Networks

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 536
Author(s):  
Shaojian He ◽  
Zhongrui Lu ◽  
Wenxu Dai ◽  
Kangning Yang ◽  
Yang Xue ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Composite Membrane ◽  
Proton Transport ◽  
Phosphotungstic Acid ◽  
Three Dimensional ◽  
Water Soluble ◽  
Hydroxyl Groups ◽  
Transport Networks ◽  
Hybrid Fillers ◽  
Speek Membrane

Phosphotungstic acid (HPW)-filled composite proton exchange membranes possess high proton conductivity under low relative humidity (RH). However, the leaching of HPW limits their wide application. Herein, we propose a novel approach for anchoring water soluble phosphotungstic acid (HPW) by polydopamine (PDA) coated graphene oxide and halloysite nanotubes (DGO and DHNTs) in order to construct hybrid three-dimensional proton transport networks in a sulfonated poly(ether ether ketone) (SPEEK) membrane. The introduction of PDA on the surfaces of the hybrid fillers could provide hydroxyl groups and secondary amine groups to anchor HPW, resulting in the uniform dispersion of HPW in the SPEEK matrix. The SPEEK/DGO/DHNTs/HPW (90/5/5/60) composite membrane exhibited higher water uptake and much better conductivity than the SPEEK membrane at low relative humidity. The best conductivity reached wass 0.062 S cm−1 for the composite membrane, which is quite stable during the water immersion test.

scholarly journals The Superagonistic Activity of Bovine Thyroid-stimulating Hormone (TSH) and the Human TR1401 TSH Analog Is Determined by Specific Amino Acids in the Hinge Region of the Human TSH Receptor

2009 ◽  
Vol 284 (24) ◽  
pp. 16317-16324 ◽  
Author(s):  
Sandra Mueller ◽  
Gunnar Kleinau ◽  
Mariusz W. Szkudlinski ◽  
Holger Jaeschke ◽  
Gerd Krause ◽  
...  
Keyword(s):  
Amino Acids ◽  
Thyroid Stimulating Hormone ◽  
Hinge Region ◽  
Camp Production ◽  
Glycoprotein Hormone ◽  
Charged Amino Acids ◽  
Bovine Thyroid ◽  
Positively Charged ◽  
Bovine Tsh ◽  
Signaling Activity

Bovine TSH (bTSH) has a higher affinity to the human TSHR (hTSHR) and a higher signaling activity than human TSH (hTSH). The molecular reasons for these phenomena are unknown. Distinct negatively charged residues (Glu297, Glu303, and Asp382) in the hinge region of the hTSHR are known to be important for bTSH binding and signaling. To investigate the potential relevance of these positions for differences between bTSH and hTSH in the interaction to the hTSHR, we determined bTSH- and hTSH-mediated cAMP production of several substitutions at these three hinge residues. To examine specific variations of hTSH, we also investigated the superagonistic hTSH analog TR1401 (TR1401), whose sequence differs from hTSH by four additional positively charged amino acids that are also present in bTSH. To characterize possible interactions between the acidic hTSHR positions Glu297, Glu303, or Asp382 and the additional basic residues of TR1401, we investigated TR1401 binding and signaling properties. Our data reveal increased cAMP signaling of the hTSHR using TR1401 and bTSH compared with hTSH. Whereas Asp382 seems to be important for bTSH- and TR1401-mediated but not for hTSH-mediated signaling, the substitution E297K exhibits a decreased signaling for all three TSH variants. Interestingly, bTSH and TR1401 showed only a slightly different binding pattern. These observations imply that specific residues of the hinge region are mediators of the superagonistic activity of bTSH and TR1401 in contrast to hTSH. Moreover, the simultaneous localization of binding components in the glycoprotein hormone molecule and the receptor hinge region permits important reevaluation of interacting hormone receptor domains.

scholarly journals The principle of formaldehyde, alcohol, and acetone titrations. With a discussion of the proof and implication of the zwitterion conception

1934 ◽  
Vol 115 (792) ◽  
pp. 121-141 ◽  
Keyword(s):  
Amino Acids ◽  
Carboxyl Groups ◽  
Recent Discussion ◽  
Amino Groups ◽  
Chemical Methods ◽  
Titration Method ◽  
Physico Chemical ◽  
Empirical Argument ◽  
Chemical Evidence

Consideration of the implications of the zwitterion hypothesis of Bjerrum (1923) makes it desirable to state afresh the principles underlying the methods commonly employed in the titration of amino-acids. Deductions of considerable theoretical importance, cf., e. g ., Calvery (1933) are still being made on the supposition that the alkalimetric formaldehyde titration method of Sørensen (1907) and the corresponding alcohol method of Foreman (1920) and of Willstätter and Waldschmidt-Leitz (1921) estimate the carboxyl groups of amino-acids whilst the acidimetric acetone titration of Linderstrøm-Lang (1928) estimates the amino-groups. Yet the zwitterion hypothesis indicates that this assumption is the reverse of the truth. Discussion is greatly facilitated by collective consideration of recent physico-chemical evidence clarifying the principles upon which these common bio-chemical methods rest. In a recent discussion of two of the titrimetric methods (Van Slyke and Kirk, 1933) the existence of this evidence is ignored, so that it becomes necessary to systematize and elaborate the empirical argument of these authors in the light of the relevant investigations of Grünhut (1919), Cray and Westrip (1925), Michaelis and Mizutani (1925), Birch and Harris (1930, b ), and Levy (1933). At the same time new and useful developments are indicated.

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