scholarly journals Calcium binding by human erythrocyte membranes. Significance of carboxyl, amino and thiol groups

1971 ◽  
Vol 125 (1) ◽  
pp. 343-352 ◽  
Author(s):  
Janet Forstner ◽  
J. F. Manery
Keyword(s):  
Glutamic Acid ◽  
Aspartic Acid ◽  
Calcium Binding ◽  
Major Effect ◽  
Water Soluble ◽  
Erythrocyte Membranes ◽  
Molar Ratio ◽  
Carboxyl Groups ◽  
Amino Groups ◽  
Free Carboxyl

1. The role of the ionized carboxyl groups of proteins of the erythrocyte membrane as Ca2+ receptor sites was investigated. A water-soluble carbodi-imide [1-cyclohexyl-3-(2-morpholinoethyl)carbodi-imide methotoluene-p-sulphonate], referred to as carbodi-imide reagent, and glycine methyl ester were used to modify the free carboxyl groups of the membrane. The degree of modification was estimated from amino acid analyses, which showed the amount of glycine incorporated. As the concentration of carbodi-imide reagent was raised (0.1–0.4m) incorporation of glycine increased and Ca2+ binding decreased by about 77%. At 0.4m-carbodi-imide reagent all of the binding of Ca2+ to protein was abolished and it was estimated that about 37% of the side-chain carboxyl groups of aspartic acid plus glutamic acid had been blocked by glycine. 2. Acetylation of all of the free amino groups was achieved by incubating the erythrocyte ‘ghosts’ at pH10.3 with acetic anhydride (10–15mg/10mg of ‘ghost’ protein). Acetylation increased by 1.5-fold the capacity of the ‘ghost’ to bind Ca2+, indicating that the remaining carboxyl groups of aspartic acid and glutamic acid were made available for Ca2+ binding by this procedure. These findings support the concept that in normal ‘ghosts’, at pH7.4, Ca2+ binding to free carboxyl groups is partially hindered by the presence of charged amino groups. 3. Treatment of ‘ghosts’ with N-acetylneuraminidase, which removed 94% of sialic acid residues, and treatment with 1mm-p-chloromercuribenzoate did not alter Ca2+ binding. The major effect of 5.8mm-p-chloromercuribenzoate upon ‘ghosts’ was to cause a solubilization of a calcium–membrane complex, which included about one-third of the ‘ghosts’ protein. The molar ratio of Ca2+: protein in the solubilized material was the same as that in the intact (untreated) ‘ghosts’.

scholarly journals Positive Charges on Lysine Residues of the Extrinsic 18 kDa Protein Are Important to Its Electrostatic Interaction with Spinach Photosystem II Membranes

2005 ◽  
Vol 37 (11) ◽  
pp. 737-742 ◽  
Author(s):  
Jin-Peng Gao ◽  
Zhen-Hua Yong ◽  
Feng Zhang ◽  
Kang-Cheng Ruan ◽  
Chun-He Xu ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Methyl Esters ◽  
Binding Activity ◽  
Water Soluble ◽  
Carboxyl Groups ◽  
Amino Groups ◽  
Charged Amino Acids ◽  
Lysine Residues ◽  
Glycine Methyl Ester ◽  
Positively Charged

Abstract To determine the contribution of charged amino acids to binding with the photosystem II complex (PSII), the amino or carboxyl groups of the extrinsic 18 kDa protein were modified with Nsuccinimidyl propionate (NSP) or glycine methyl ester (GME) in the presence of a water-soluble carbodiimide, respectively. Based on isoelectric point shift, 4–10 and 10–14 amino groups were modified in the presence of 2 and 4 mM NSP, respectively. Similarly, 3–4 carboxyl groups were modified by reaction with 100 mM GME. Neutralization of negatively charged carboxyl groups with GME did not alter the binding activity of the extrinsic 18 kDa protein. However, the NSP-modified 18 kDa protein, in which the positively charged amino groups had been modified to uncharged methyl esters, failed to bind with the PSII membrane in the presence of the extrinsic 23 kDa protein. This defect can not be attributed to structural or conformational alterations imposed by chemical modification, as the fluorescence and circular dichroism spectra among native, GME and NSP-modified extrinsic 18 kDa proteins were similar. Thus, we have concluded that the positive charges of lysyl residues in the extrinsic 18 kDa protein are important for its interaction with PSII membranes in the presence of the extrinsic 23 kDa protein. Furthermore, it was found that the negative charges of carboxyl groups of this protein did not participate in binding with the extrinsic 23 kDa protein associated with PSII membranes.

STUDIES ON WHEAT PLANTS USING C14 COMPOUNDS: VII. UTILIZATION OF PYRUVATE-2-C14

1958 ◽  
Vol 36 (1) ◽  
pp. 381-388 ◽  
Author(s):  
E. Bilinski ◽  
W. B. McConnell
Keyword(s):  
Amino Acids ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Active Carbon ◽  
Specific Activity ◽  
Carboxyl Groups ◽  
Gluten Protein ◽  
Carbon 14 ◽  
Soluble Material

Approximately half of the carbon-14 injected into the stems of wheat plants in the form of pyruvate-2-C14 remained in the plant at maturity, 30 days later. Almost 90% of this had accumulated in the kernel. Appreciable activity was found in the major components, protein, starch, ether-soluble material, and a residue termed bran. The amino acids of the gluten protein differed markedly from one another in specific activity. Glutamic acid and the related amino acids, arginine and proline, were most active, their specific activity decreasing in that order. Fifty-two per cent of the carbon-14 in glutamic acid was in carbon-5, while carbon-1 contained 21%. Seventy per cent of the radioactivity of aspartic acid was divided almost equally between the terminal carboxyl groups. The results are similar to those previously observed using acetate-1-C14 as tracer, and it is concluded that administered pyruvate-2-C14 undergoes extensive decarboxylation to form acetate-1-C14. The most active carbon in alanine from the pyruvate-2-C14 was carbon-1. This observation is not in accord with the theory that alanine is formed directly from pyruvate by transamination.

Sequence Determination of a Protein with N-Terminal Glutamic Acid after Modification of Carboxyl Groups with Carbodiimide as the Coupling Agent

1974 ◽  
Vol 52 (6) ◽  
pp. 560-562
Author(s):  
C. Gilardeau ◽  
M. Chrétien
Keyword(s):  
Methyl Ester ◽  
Glutamic Acid ◽  
Water Soluble ◽  
Carboxyl Groups ◽  
Edman Degradation ◽  
Sequence Determination ◽  
Glutamic Acid Residue ◽  
N Terminus ◽  
Glycine Methyl Ester

Glutamine and asparagine residues in proteins can be differentiated from glutamic and aspartic residues, during the Edman degradation, after modification of the carboxyl groups by glycine methyl ester in presence of a water-soluble carbodiimide. When applied to ovine and porcine beta-lipotropic hormones, which have a glutamic acid residue at the N-terminus, the carbodiimide blocks the N-terminus. However, the Edman degradation proceeds normally, if the phenylthiocarbamyl derivative is formed prior to the modification reaction with glycine. In this communication, radioactive glycine was used to modify the carboxyl groups.

scholarly journals Hyaluronic acid in the pulmonary secretions of patients with asthma

1978 ◽  
Vol 173 (2) ◽  
pp. 565-568 ◽  
Author(s):  
S Sahu ◽  
W S Lynn
Keyword(s):  
Amino Acids ◽  
Hyaluronic Acid ◽  
Glutamic Acid ◽  
Cellulose Acetate ◽  
Aspartic Acid ◽  
Molar Ratio ◽  
Cellulose Acetate Electrophoresis ◽  
Single Spot ◽  
Testicular Hyaluronidase

Hyaluronic acid was the only glycosaminoglycan found in the pulmonary secretions of patients with asthma. The compound had a hexuronate/hexosamine molar ratio of about 1:1. Glucosamine constituted over 98% of the hexosamines, the remaining being galactosamine. The compound moved as a single spot with the mobility of standard hyaluronic acid on cellulose acetate electrophoresis, and this spot disappeared after digestion with testicular hyaluronidase. Even after extensive proteolysis and purification, the compound was associated with small amounts of protein, the major amino acids of which were aspartic acid, threonine, serine, glutamic acid, glycine and valine.

scholarly journals Terminal Amino Groups in Wool and S-Carboxymethyl Kerateine 2

1957 ◽  
Vol 10 (2) ◽  
pp. 225 ◽  
Author(s):  
EOP Thompson
Keyword(s):  
Amino Acid ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Amino Groups ◽  
Terminal Amino Acid ◽  
Total N ◽  
Purified Protein Derivative ◽  
Terminal Residue ◽  
Terminal Amino

The N-terminal residues of Merino 64's quality wool and of a purified protein derivative extracted from it, S-carboxymethyl kerateine 2, have been determined. A similar total N-terminal residue content is present in both wool and S�carboxymethyl kerateine 2 comprising glycine, serine, threoni~e, aspartic acid, glutamic acid, and alanine. These occur in different proportions in the two materials and valine is an additional N-terminal amino acid present only in wool.

STUDIES ON WHEAT PLANTS USING C14 COMPOUNDS: VII. UTILIZATION OF PYRUVATE-2-C14

1958 ◽  
Vol 36 (4) ◽  
pp. 381-388 ◽  
Author(s):  
E. Bilinski ◽  
W. B. McConnell
Keyword(s):  
Amino Acids ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Active Carbon ◽  
Specific Activity ◽  
Carboxyl Groups ◽  
Gluten Protein ◽  
Carbon 14 ◽  
Soluble Material

Approximately half of the carbon-14 injected into the stems of wheat plants in the form of pyruvate-2-C14 remained in the plant at maturity, 30 days later. Almost 90% of this had accumulated in the kernel. Appreciable activity was found in the major components, protein, starch, ether-soluble material, and a residue termed bran. The amino acids of the gluten protein differed markedly from one another in specific activity. Glutamic acid and the related amino acids, arginine and proline, were most active, their specific activity decreasing in that order. Fifty-two per cent of the carbon-14 in glutamic acid was in carbon-5, while carbon-1 contained 21%. Seventy per cent of the radioactivity of aspartic acid was divided almost equally between the terminal carboxyl groups. The results are similar to those previously observed using acetate-1-C14 as tracer, and it is concluded that administered pyruvate-2-C14 undergoes extensive decarboxylation to form acetate-1-C14. The most active carbon in alanine from the pyruvate-2-C14 was carbon-1. This observation is not in accord with the theory that alanine is formed directly from pyruvate by transamination.

scholarly journals THE CONDUCTIVITIES OF AQUEOUS SOLUTIONS OF GLYCINE, d,l-VALINE, AND l-ASPARAGINE

1935 ◽  
Vol 18 (4) ◽  
pp. 467-479 ◽  
Author(s):  
John W. Mehl ◽  
Carl L. A. Schmidt
Keyword(s):  
Aqueous Solutions ◽  
Glutamic Acid ◽  
Potassium Chloride ◽  
Aspartic Acid ◽  
Dissociation Constants ◽  
Carboxyl Groups ◽  
Similar Data ◽  
Conductivity Data ◽  
Ionic Atmosphere ◽  
Theoretical Considerations

1. The conductivities of aqueous solutions of glycine, d,l-valine, and l-asparagine have been determined, and comparisons have been made with similar data reported in the literature. 2. On the basis of certain theoretical considerations, calculations of the expected conductivities of aqueous solutions of glycine, asparagine, aspartic acid, and glutamic acid have been made and these data have been compared with similar data obtained experimentally. 3. The dissociation constants of the carboxyl groups of aspartic acid and glutamic acid have been calculated from conductivity data. 4. It is shown that alanine has no effect on the ionic atmosphere of solutions of potassium chloride.

Solubility Enhancement of the Poorly Water-Soluble Antiulcer Drug Famotidine by Inclusion Complexation

2013 ◽  
Vol 6 (1) ◽  
pp. 1983-1989 ◽  
Author(s):  
Shabnam Ain ◽  
V Gupta ◽  
Babita K ◽  
Q Ain ◽  
J Dahiya
Keyword(s):  
Inclusion Complex ◽  
Dissolution Rate ◽  
Phosphate Buffer ◽  
Physical Mixture ◽  
Water Soluble ◽  
Molar Ratio ◽  
Phase Solubility ◽  
Distilled Water ◽  
Physicochemical Interaction ◽  
Mixture Phase

Aqueous solubility is a critical factor for optimum drug delivery. In the present study, we investigated the potential of drug-cyclodextrin complexation as an approach for improving the solubility and bioavailability of famotidine, an H2-receptor antagonist and acid reducing drug which has poor solubility and bioavailability. Solubility improvement of drug by β-cyclodextrin was done by simple complexation approach using physical, kneading and co-precipitation methods and compared with physical mixture. Phase solubility profile indicated that the solubility of famotidine was significantly increased in presence of β-cyclodextrin and shows a linear graph with β-cyclodextrin indicating formation of inclusion complexes in a 1:1 molar ratio. β-Cyclodextrin-famotidine mixture have maximum stability constant 1477.6 M-1. The inclusion complex ratio 1:1 of kneading mixture was selected based on drug release profile and compared with physical mixture. Further characterization was done by  using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) to identify the physicochemical interaction between drug and carrier and its effect on dissolution. Dissolution rate studies for selected inclusion complex was performed in 0.1 N HCl (pH 1.2), phosphate buffer (pH 7.5) and distilled water (pH 6.8) and compared these to pure drug profile which was found to be 2.34 fold increase in distilled water, 1.83 fold in HCl and 2.01 fold in phosphate buffer (pH 7.5). These results suggest that the kneaded complex of famotidine with β-cyclodextrin as hydrophilic complexation agent can substantially enhance the solubility and dissolution rate. Such complex has promising potential to improve the bioavailability of famotidine.  

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