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.

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 The oxygen-linked zinc-binding site of human haemoglobin

1978 ◽  
Vol 169 (3) ◽  
pp. 625-632 ◽  
Author(s):  
J G Gilman ◽  
G J Brewer
Keyword(s):  
Binding Sites ◽  
Zinc Ion ◽  
Bohr Effect ◽  
Zinc Binding ◽  
Hill Coefficient ◽  
Human Haemoglobin ◽  
Equilibrium Binding ◽  
Zinc Binding Site ◽  
Alkaline Bohr Effect ◽  
The Hill

Zn2+ is known to increase the 02 affinity of human haemoglobin. Previous data suggested that Zn2+ exerts its effect by directly binding to haemoglobin, rather than by competing with or binding to 2,3-bisphosphoglycerate. It was also shown that there are two 02-linked zinc-binding sites in haemoglobin, and that Zn2+ does not significantly alter haemoglobin co-operativity or the alkaline Bohr effect. The effect of Zn2+ on 02 affinity of haemoglobin can also be observed for other haemoglobins as diverse as those of cow and chicken. This paper presents new data on the haemoglobin-zinc interaction for normal haemoglobin, des-His146beta-haemoglobin and N-ethylsuccinimide-haemoglobin of humans. For normal haemoglobin (0.05 mM in tetramers), at 20 degrees C in buffer containing 0.1 M-Cl-, 02-dissociation-curve experiments showed that the addition of 0.4-0.5 mM-ZnS04 did not change the Bohr effect between pH 6.71 and 7.29. Similar experiments, with “zinc-ion buffers”, showed that the value of the Hill coefficient, h, decreased only slightly if the concentration of free Zn2+ was held constant. For N-ethylsuccinimide-haemoglobin, Zn2+ caused less increase in O2 affinity than for normal haemoglobin. These studies, together with data on the equilibrium binding of Zn2+ to oxy-, deoxy- and des-His146beta-haemoglobins, suggest that zinc is chelated in oxyhaemoglobin by at least three amino acids, two of which are histidine-146beta and cysteine-93beta.

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.

Comparative Two-Dimensional Gel Electrophoresis of Trypanosoma cruzi Mammalian-Stage Forms in an Alkaline pH Range

2015 ◽  
Vol 22 (12) ◽  
pp. 1066-1075 ◽  
Author(s):  
Adriana Magalhães ◽  
Rayner Queiroz ◽  
Izabela Bastos ◽  
Jaime Santana ◽  
Marcelo Sousa ◽  
...  
Keyword(s):  
Trypanosoma Cruzi ◽  
Gel Electrophoresis ◽  
Two Dimensional ◽  
Alkaline Ph ◽  
Two Dimensional Gel Electrophoresis ◽  
Ph Range

scholarly journals Carp hemoglobin. II. The alkaline Bohr effect.

1980 ◽  
Vol 255 (20) ◽  
pp. 9800-9806
Author(s):  
J.C. Chien ◽  
K.H. Mayo
Keyword(s):  
Bohr Effect ◽  
Alkaline Bohr Effect

A method for estimation of urea using ammonia electrode and its applicability to milk samples

2008 ◽  
Vol 75 (4) ◽  
pp. 466-470 ◽  
Author(s):  
Rajan Sharma ◽  
Yudhishthir S Rajput ◽  
Sumandeep Kaur ◽  
Sudhir K Tomar
Keyword(s):  
Carbon Dioxide ◽  
Sodium Azide ◽  
Inverse Relationship ◽  
Ammonium Ion ◽  
Enzymatic Method ◽  
Alkaline Ph ◽  
Milk Samples ◽  
Electrode Response ◽  
Urease Enzyme ◽  
Ammonia Electrode

A method for the estimation of urea in milk using ammonia electrode is described. Urea is first degraded by urease enzyme into ammonium ion and carbon dioxide at neutral pH. The ammonium ion is then converted into ammonia at alkaline pH. A linear inverse relationship was observed between logarithmic concentration of ammonia or urea and electrode response. Repeatability, expressed as a coefficient of variation, was 1·77% at a level of 8·92 mm-urea in milk. The method was validated in milk samples spiked with between 2×10−3 and 10×10−3 m-urea and recovery of added urea was quantitative. Whereas, preservative sodium azide at 0·5 g/l or 2 g/l level did not affect results, lower values of urea concentration in presence of Bronopol at 0·5 g/l were observed. Urea levels in milk samples estimated by this method were comparable to standard enzymatic method. The method is simple, fast and is not prone to interference from other milk constituents.

The Significance of the Bohr Effect in the Respiration and Asphyxiation of the Squid, Loligo Pealei

1929 ◽  
Vol 6 (4) ◽  
pp. 340-349 ◽  
Author(s):  
ALFRED C. REDFIELD ◽  
ROBERT GOODKIND
Keyword(s):  
Carbon Dioxide ◽  
Toxic Effect ◽  
Venous Blood ◽  
Bohr Effect ◽  
Reciprocal Effects ◽  
Cent Oxygen ◽  
Carbon Dioxide Content ◽  
Arterial Blood ◽  
Loligo Pealei

1. The oxygen and carbon-dioxide content of the arterial and venous blood of the squid, Loligo pealei, have been measured. 2. Using a nomographic method of analysis it is shown that the reciprocal effects of oxygen and carbon dioxide upon the respiratory properties of squid haemocyanin account for one-third of the respiratory exchange. 3. The venous blood is estimated to be 0.13 pH unit more acid than the arterial blood. 4. Death from asphyxiation occurs when the oxygen and carbon-dioxide pressures are such that the arterial blood can combine with only 0.5 to 1.5 volumes per cent, oxygen. Carbon dioxide exerts no toxic effect except through its influence on the oxygenation of the blood. 5. The haemocyanin of the blood is of vital necessity to the squid, because the amount of oxygen which can be physically dissolved in blood is less than the amount which is necessary for the maintenance of life.

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