Unusual chemical properties of the amino groups of insulin: implications for structure–function relationship

1979 ◽  
Vol 57 (6) ◽  
pp. 489-496 ◽  
Author(s):  
Marla G. Sheffer ◽  
Harvey Kaplan
Keyword(s):  
Carbon Dioxide ◽  
Acetic Anhydride ◽  
Chemical Properties ◽  
Amino Terminus ◽  
Amino Group ◽  
Amino Groups ◽  
Ph Values ◽  
Function Relationship ◽  
Ph Range ◽  
Association State

The chemical properties of the three amino groups of insulin were obtained at 10 and 37 °C using the competitive labelling technique with acetic anhydride as the labelling reagent. At 10 °C, pK values of 7.9, 7.2, and 7.8 were found for the glycyl A1, phenylalanyl B1, and lysyl B29 amino groups. When compared with standard amino compounds by means of a Brønsted plot, the two amino-termini were found to be 'super-reactive' and the lysyl ε-amino group buried. In the presence of carbon dioxide at physiological pH values, all three amino groups became much less reactive indicating that they had reacted to form carbamino derivatives. Above pH 8 the reactivities of the glycyl amino terminus and ε-amino group increase sharply indicating that insulin is undergoing a conformational change which is most likely a change in its association state. At 37 °C the amino groups do not titrate normally but exhibit sharp increases in reactivity over the physiological pH range with the midpoints in the pH reactivity profiles between pH values of 7.0 and 7.3. This behaviour is interpreted as a rapid disaggregation of insulin to form monomers as a result of the ionization of the amino groups. It is concluded that at physiological pH and temperature all three amino groups are deprotonated.

scholarly journals Chemical properties of the N-termini of human haemoglobin

1982 ◽  
Vol 203 (2) ◽  
pp. 435-443 ◽  
Author(s):  
H Kaplan ◽  
P A Hamel ◽  
A M L Chan ◽  
G Oda
Keyword(s):  
Acetic Anhydride ◽  
Conformational Change ◽  
Chemical Properties ◽  
High Reactivity ◽  
Alkaline Ph ◽  
Amino Groups ◽  
Human Haemoglobin ◽  
Ph Values ◽  
Ph Dependent ◽  
Alkaline Bohr Effect

The chemical properties, namely pK and reactivity, of the N-termini of oxyhaemoglobin and deoxyhaemoglobin toward acetic anhydride and 1-fluoro-2,4-dinitrobenzene (Dnp-F) were determined by the competitive-labelling approach [Kaplan, Stevenson & Hartley, (1971) Biochem. J. 124, 289-229; Duggleby & Kaplan (1975) Biochemistry 14, 5168-5175]. At physiological pH and temperature, the valine-1 alpha and valine-1-beta amino groups had unusually low pK values, but showed only minimal changes in their pK values on deoxygenation. Between pH 7.5 and pH 8.0 a deviation was observed in the pH-reactivity profiles and the apparent pK values became markedly pH-dependent. It was found that Dnp-F, but not acetic anhydride, had an abnormally high reactivity toward the N-termini. It is concluded that the valine-1 alpha and valine-1 beta N-termini make little or no contribution to the alkaline Bohr effect at physiological pH values. The high reactivity toward Dnp-F is attributed to an interaction or binding near the N-terminal region, and the discontinuity in the pH-reactivity profile at moderate alkaline pH values to a conformational change which alters the environment of these groups.

scholarly journals Unmasking of histone amino groups in chromatin at high pH

1976 ◽  
Vol 159 (1) ◽  
pp. 173-175 ◽  
Author(s):  
B L Malchy ◽  
H Kaplan
Keyword(s):  
Acetic Anhydride ◽  
Amino Groups ◽  
High Ph ◽  
Ph Values ◽  
Ph Range

The reactivity of the amino groups of histones in chromatin towards acetic anhydride was determined as a function of pH. In the pH range 7-10 the vast majority of amino groups in all five histones are buried. However, at higher pH values some of the histone amino groups become exposed, and the higher the lysine:arginine ratio for the histone the greater was the degree of unmasking observed. At pH 11.8 histone I appears to be completely dissociated, histones IIB1 and IIb2 have approx. 55% of the amino groups unmasked, and histones III and IV have approx. 25% of the amino groups unmasked.

scholarly journals The binding of carbon dioxide by horse haemoglobin

1971 ◽  
Vol 124 (1) ◽  
pp. 31-45 ◽  
Author(s):  
J. V. Kilmartin ◽  
L. Rossi-Bernardi
Keyword(s):  
Carbon Dioxide ◽  
Bohr Effect ◽  
Alkaline Ph ◽  
Amino Groups ◽  
Expected Number ◽  
Physiological Conditions ◽  
Alkaline Bohr Effect ◽  
Ph Range ◽  
The Hill ◽  
Β Chain

1. Three modified horse haemoglobins have been prepared: (i) αc2βc2, in which both the α-amino groups of the α- and β-chains have reacted with cyanate, (ii) αc2β2, in which the α-amino groups of the α-chains have reacted with cyanate, and (iii) α2βc2, in which the two α-amino groups of the β-chain have reacted with cyanate. 2. The values of n (the Hill constant) for αc2βc2, α2βc2 and αc2β2 were (respectively) 2.5, 2.0 and 2.6, indicating the presence of co-operative interactions between the haem groups for all derivatives. 3. In the alkaline pH range (about pH8.0) all the derivatives show the same charge as normal haemoglobin whereas in the acid pH range (about pH6.0) αc2βc2 differs by four protonic charges and αc2β2, α2βc2 by two protonic charges from normal haemoglobin, indicating that the expected number of ionizing groups have been removed. 4. αc2β2 and αc2βc2 show a 25% decrease in the alkaline Bohr effect, in contrast with α2βc2, which has the same Bohr effect as normal haemoglobin. 5. The deoxy form of αc2βc2 does not bind more CO2 than the oxy form of αc2βc2, whereas αc2β2 and α2βc2 show intermediate binding. 6. The results reported confirm the hypothesis that, under physiological conditions, haemoglobin binds CO2 through the four terminal α-amino groups and that the two terminal α-amino groups of α-chains are involved in the Bohr effect.

scholarly journals Different reactivities of free and bound amino groups in deoxy-and liganded haemoglobin

1977 ◽  
Vol 163 (2) ◽  
pp. 393-395 ◽  
Author(s):  
D Bresciani
Keyword(s):  
Acetic Anhydride ◽  
Double Labelling ◽  
Amino Group ◽  
Salt Bridges ◽  
Amino Groups

The technique of competitive double-labelling [H. Kaplan, K.J. Stevenson & B.S. Hartley, (1971) Biochem. J. 124, 289-299; L.P. Visentin & H. Kaplan (1975) Biochemistry 14, 463-468] was used to determine the reactivity of some amino groups towards acetic anhydride in deoxy-and liganded haemoglobin. Only those amino groups known to form salt bridges in deoxy-but not in liganded haemoglobin (i.e. the alpha-amino group of valine-1 alpha and the xi-amino group of lysine-40 alpha and lysine-127 alpha [M. F. Perutz (1970) Nature (London) 228, 726-739]) and different reactivities in the two structures.

Formation of borate complexes of inosamines (aminodeoxyinositols) and their separation by paper electrophoresis

1974 ◽  
Vol 27 (4) ◽  
pp. 853 ◽  
Author(s):  
JL Frahn ◽  
JA Mills
Keyword(s):  
Carbon Dioxide ◽  
Paper Electrophoresis ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Amino Group ◽  
Ph Values ◽  
Borate Complex ◽  
Wide Range ◽  
Borate Complexes ◽  
Probable Site

The electrophoretic mobility of an inosamine in borate buffer is very dependent on configuration, and a set of 10 inosamines showed a wide range of mobilities. The order of mobilities within the set changed as the pH of the buffer was changed in the range 7.7-9.5. Paper electrophoresis in borate buffers can effectively separate mixtures of inosamines. The probable site of reaction between an inosamine and borate ions has been identified for some isomers. In aminodeoxy-scyllo-inositol and 3-amino-3-deoxy-epi-inositol the amino group is involved in the formation of a tridentate borate complex of adamantane-type structure, which is electrically neutral over the above range of pH values. Aminodeoxy-scyllo-inositol simultaneously combines with a second molecule of borate, forming a bis-tridentate complex with one anionic centre. There is evidence that in other isomers protonation of the amino group and formation of anionic borate complexes at hydroxyl groups are not independent reactions. Paper electrophoresis in non-complexing buffers provides evidence for the relative basicities of inosamines. DL-2-Amino-2-deoxy-epi-inositol, which has an interaction between axial amino and hydroxyl group in the preferred conformation, was the strongest base in the set, whereas the bases with an axial amino group free of such an interaction were the weakest. Inosamines form N-carboxyl derivatives in the normal way on exposure to carbon dioxide in the presence of strong alkali.

scholarly journals Reactivity and Ionization Constants of the Lysine Residues in Apovitellenin I of Emu Egg Yolk Low-density Lipoprotein by Competitive Labelling

1975 ◽  
Vol 28 (6) ◽  
pp. 433
Author(s):  
Theo AA Dopheide
Keyword(s):  
Acetic Anhydride ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Egg Yolk ◽  
Ionization Constants ◽  
Low Density ◽  
Amino Groups ◽  
Ph Values ◽  
Titration Curves ◽  
Lysine Residues

Competitive labelling with [14C]acetic anhydride over a range of pH values has been used to explore the surface topography of the apovitellenin I moiety in emu egg yolk low-density lipoprotein. The reaction of the lysine e-amino groups with acetic anhydride has been related to pH in a set of titration curves; from these, the reactivities relative to alanine and the ionization constants of all but the amino terminallysines have been determined.

Reaction with acetic anhydride as a method for estimating the basicity of exocyclic amino groups in nitrogen heterocycles

1984 ◽  
Vol 37 (8) ◽  
pp. 1625 ◽  
Author(s):  
LW Deady ◽  
WL Finlayson
Keyword(s):  
Acetic Anhydride ◽  
Nitrogen Heterocycles ◽  
Amino Group ◽  
Amino Groups ◽  
Substituted Anilines ◽  
Pka Values

Relative rates for acetylation of various anilines and amino heterocycles with acetic anhydride in pyridine were determined by a competition method. From a Bronsted plot of reactivity against basicity for the anilines, and by considering the heterocycles as substituted anilines, pKa values for the amino group in a variety of heterocycles have been obtained.

Effect of lime application to strongly acidic soils on the growth of macadamia seedlings

1990 ◽  
Vol 30 (3) ◽  
pp. 421
Author(s):  
RL Aitken ◽  
RA Stephenson ◽  
EC Gallagher
Keyword(s):  
Seedling Growth ◽  
Soil Ph ◽  
Sandy Loam ◽  
Chemical Properties ◽  
Calcium Deficiency ◽  
Silty Clay ◽  
Micronutrient Deficiencies ◽  
Acidic Soils ◽  
Ph Values ◽  
Ph Range

Glasshouse experiments were undertaken to evaluate the effects of soil pH on macadamia (Macadamia integrifolia Maiden and Betche) seedlings and to examine seedling growth in relation to soil chemical properties in acidic soils. In one experiment, in which 13 rates of CaCO3 (0 to the equivalent of 12 000 kg/ha) were applied to a strongly acidic (pH 3.9, 1:5 in water) sandy loam, optimum seedling growth was obtained in the pH range 4.0-5.9. A second experiment, in which seedlings were grown in each of 3 strongly acidic soils amended with various rates of CaCO3, also showed that macadamia seedlings could grow satisfactorily at pH values of 4.0 (2 soils) and 4.5 (1 soil). Increased seedling growth on 2 soils (silty clay loam, experiment 1; sandy loam, experiment 2) treated with lime was due to amelioration of aluminium and/or manganese toxicity and not to the alleviation of calcium deficiency. The results indicate that soil pH measurement alone would not be a good indicator of seedling growth. In some soils, seedling growth was optimum at pH 3.9, whereas at pH 4.0 in another soil, growth was well below the maximum which was attained at pH 4.5. The significant (P<0.05) growth reductions that occurred on all soils limed to pH values >6.0 were attributed to induced micronutrient deficiencies.

scholarly journals Formation of Hg(II) tetrathiolate complexes with cysteine at neutral pH

2016 ◽  
Vol 94 (4) ◽  
pp. 373-379 ◽  
Author(s):  
Thomas Warner ◽  
Farideh Jalilehvand
Keyword(s):  
Spectroscopic Techniques ◽  
Amino Groups ◽  
Dilute Solutions ◽  
Concentrated Solutions ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Ph Values ◽  
Lower Charge ◽  
Ph Range ◽  
X Ray Absorption

Mercury(II) ions precipitate from aqueous cysteine (H2Cys) solutions containing H2Cys/Hg(II) mole ratio ≥ 2.0 as Hg(S-HCys)2. In the absence of additional cysteine, the precipitate dissolves at pH ∼12 with the [Hg(S,N-Cys)2]2– complex dominating. With excess cysteine (H2Cys/Hg(II) mole ratio ≥ 4.0), higher complexes form and the precipitate dissolves at lower pH values. Previously, we found that tetrathiolate [Hg(S-Cys)4]6– complexes form at pH = 11.0; in this work, we extend the investigation to pH values of physiological interest. We examined two series of Hg(II)–cysteine solutions in which CHg(II) varied between 8 and 9 mmol/L and 80 and 100 mmol/L, respectively, with H2Cys/Hg(II) mole ratios from 4 to ∼20. The solutions were prepared in the pH range 7.1–8.8 at the pH at which the initial Hg(S-HCys)2 precipitate dissolved. The variations in the Hg(II) speciation were followed by 199Hg NMR, X-ray absorption, and Raman spectroscopic techniques. Our results show that in the dilute solutions (CHg(II) = 8–9 mmol/L), mixtures of di-, tri- (major), and tetrathiolate complexes exist at moderate cysteine excess (CH2Cys ∼0.16 mol/L) at pH 7.1. In the more concentrated solutions (CHg(II) = 80–100 mmol/L) with high cysteine excess (CH2Cys > 0.9 mol/L), tetrathiolate [Hg(S-cysteinate)4]m−6 (m = 0–4) complexes dominate in the pH range 7.3–7.8, with lower charge than for the [Hg(S-Cys)4]6– complex due to protonation of some (m) of the amino groups of the coordinated cysteine ligands. The results of this investigation could provide a key to the mechanism of biosorption and accumulation of Hg(II) ions in biological/environmental systems.

Investigation of Some Water Quality Parameters of Pond Water under Mymensingh Municipality

2015 ◽  
Vol 8 (1) ◽  
pp. 85-89
Author(s):  
F Zannat ◽  
MA Ali ◽  
MA Sattar
Keyword(s):  
Water Quality ◽  
Water Samples ◽  
Chemical Properties ◽  
Pond Water ◽  
Quality Parameters ◽  
Water Quality Parameters ◽  
Urban Region ◽  
Mn Toxicity ◽  
Ph Values ◽  
Drinking Water Standard

A study was conducted to evaluate the water quality parameters of pond water at Mymensingh Urban region. The water samples were collected from 30 ponds located at Mymensingh Urban Region during August to October 2010. The chemical analyses of water samples included pH, EC, Na, K, Ca, S, Mn and As were done by standard methods. The chemical properties in pond water were found pH 6.68 to 7.14, EC 227 to 700 ?Scm-1, Na 15.57 to 36.00 ppm, K 3.83 to 16.16 ppm, Ca 2.01 to 7.29 ppm, S 1.61 to 4.67 ppm, Mn 0.33 to 0.684 ppm and As 0.0011 to 0.0059 ppm. The pH values of water samples revealed that water samples were acidic to slightly alkaline in nature. The EC value revealed that water samples were medium salinity except one sample and also good for irrigation. According to drinking water standard Mn toxicity was detected in pond water. Considering Na, Ca and S ions pond water was safe for irrigation and aquaculture. In case of K ion, all the samples were suitable for irrigation but unsuitable for aquaculture.J. Environ. Sci. & Natural Resources, 8(1): 85-89 2015

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