On the role of amino groups and aliphatic hydroxyls in the structure of human haemoglobin

1963 ◽  
Vol 28 (12) ◽  
pp. 3290-3296
Author(s):  
Z. Vodrážka ◽  
J. Salák ◽  
J. Čejka
Keyword(s):  
Amino Groups ◽  
Human Haemoglobin

scholarly journals Crystallization and X-ray diffraction data analysis of human deoxyhaemoglobin A0 fully stripped of any anions

1999 ◽  
Vol 55 (11) ◽  
pp. 1914-1916 ◽  
Author(s):  
F. A. V. Seixas ◽  
W. F. de Azevedo ◽  
M. F. Colombo
Keyword(s):  
Diffraction Data ◽  
Oxygen Affinity ◽  
X Ray Diffraction ◽  
Structural Explanation ◽  
Human Haemoglobin ◽  
X Ray ◽  
High Resolution Structure ◽  
Allosteric Properties

In this work, initial crystallographic studies of human haemoglobin (Hb) crystallized in isoionic and oxygen-free PEG solution are presented. Under these conditions, functional measurements of the O2-linked binding of water molecules and release of protons have evidenced that Hb assumes an unforeseen new allosteric conformation. The determination of the high-resolution structure of the crystal of human deoxy-Hb fully stripped of anions may provide a structural explanation for the role of anions in the allosteric properties of Hb and, particularly, for the influence of chloride on the Bohr effect, the mechanism by which Hb oxygen affinity is regulated by pH. X-ray diffraction data were collected to 1.87 Å resolution using a synchrotron-radiation source. Crystals belong to the space group P21212 and preliminary analysis revealed the presence of one tetramer in the asymmetric unit. The structure is currently being refined using maximum-likelihood protocols.

scholarly journals Role of capping in peptide synthesis

2020 ◽  
Vol 11 (4) ◽  
pp. 5225-5228
Author(s):  
Deepshikha Verma ◽  
Pillai V N R ◽  
Giriraj Tailor
Keyword(s):  
Peptide Synthesis ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Protecting Groups ◽  
Amino Groups ◽  
Peptide Chemistry ◽  
Fmoc Spps ◽  
Reliable Methods ◽  
Important Test

Protecting groups like Fmoc and coupling both steps are essential to monitoring the Fmoc SPPS (Solid Phase Peptide Synthesis) reaction completion. Reliable methods are used to detect the unreacted number of amino groups for monitoring these two essential reaction steps of coupling and cleavage. The ability to detect the complete coupling, incomplete coupling or failure of coupling we use many colour tests in the laboratory and based on this the Fmoc peptide chemistry allows the control of the completion of the Fmoc cleavage. The most important test used is the Kaiser test and highly recommended to monitor the coupling and cleavage steps. If the result of colour tests is positive after coupling, then the second coupling should be performed. Then again use the colour test to detect the level of coupling. If the result is still slightly positive, repeat coupling with the smaller modification of reagents such as used PyBOP instead of HOBT AND HOAT. These colour tests help in revealing the presence of unreacted amino-functional groups. Thus, we need to block these free N-terminal of amino- acids which help in avoiding the making of deletion of sequence.

scholarly journals Role of the Metal Surface on the Room Temperature Activation of the Alcohol and Amino Groups of p-Aminophenol

2020 ◽  
Vol 124 (36) ◽  
pp. 19655-19665
Author(s):  
Nerea Ruiz del Árbol ◽  
Irene Palacio ◽  
Carlos Sánchez-Sánchez ◽  
Gonzalo Otero-Irurueta ◽  
José I. Martínez ◽  
...  
Keyword(s):  
Metal Surface ◽  
Room Temperature ◽  
Amino Groups ◽  
Temperature Activation

scholarly journals Oxidation of human haemoglobin by copper. Mechanism and suggested role of the thiol group of residue β-93

1977 ◽  
Vol 165 (1) ◽  
pp. 141-148 ◽  
Author(s):  
C C Winterbourn ◽  
R W Carrell
Keyword(s):  
Electron Transfer ◽  
Binding Sites ◽  
Equilibrium Dialysis ◽  
Thiol Group ◽  
Thiol Groups ◽  
Human Haemoglobin ◽  
High Affinity ◽  
Rate Determining Step ◽  
Haemoglobin Molecule

Addition of Cu(II) ions to human oxyhaemoglobin caused the rapid oxidation of the haem groups of the beta-chain. Oxidation required binding of Cu(II) to sites involving the thiol group of beta-93 residues and was prevented when these groups were blocked with iodoacetamide or N-ethylmaleimide. Equilibrium-dialysis studies showed three pairs of binding sites, two pairs with high affinity for Cu(II) and one pair with lower affinity. It was the second pair of high-affinity sites that were blocked with iodoacetamide and were involved in haem oxidation. Cu(II) oxidized deoxyhaemoglobin at least ten times as fast as oxyhaemoglobin, and analysis of rates suggested that binding rather than electron transfer was the rate-determining step. No thiol-group oxidation to disulphides occurred during the period of haem oxidation, although it did occur subsequently in the presence of oxygen, or when Cu(II) was added to methaemoglobin. It is proposed that thiol oxidation did not occur because there exists a pathway of electron transfer between the haem group and copper bound to the beta-93 thiol groups. The route for this electron transfer is discussed, as well as the implications as to the function of the beta-93 cysteine in the haemoglobin molecule.

scholarly journals Enhanced biosorption of Cr(VI) using cotton fibers coated with chitosan – role of ester bonds

2018 ◽  
Vol 78 (3) ◽  
pp. 476-486 ◽  
Author(s):  
Sergio I. Rojas ◽  
Diana C. Duarte ◽  
Sergio D. Mosquera ◽  
Felipe Salcedo ◽  
Juan P. Hinestroza ◽  
...  
Keyword(s):  
Hexavalent Chromium ◽  
Freundlich Isotherm ◽  
Kinetic Studies ◽  
Chitosan Solution ◽  
Cotton Fibers ◽  
Isotherm Models ◽  
Order Kinetic ◽  
Amino Groups ◽  
Removal Capacity

Abstract We report on the role of ester bonds in the enhanced removal of hexavalent chromium from water using cotton fibers coated with chitosan. Adsorption capacities up to five times higher than those of the unmodified fibers were observed when the cotton fibers were exposed to an NaOH, followed by citric acid (0.97 M), and a chitosan solution (2%). We found that the use of NaOH favors the formation of ester bonds over amide bonds on the surface of the cotton fibers. This increase in the surface density of ester bonds generates an increase in the amount of exposed amino groups from the chitosan, hence increasing the removal capacity of the modified fibers. Experimental results also reveal that the adsorption is induced by the electrostatic attraction between the protonated amino groups on the surface and the negatively charged chromium ions in the water. Adsorption isotherms and kinetic studies indicated that the adsorption process fits the Langmuir and the Freundlich isotherm models as well as the pseudo-first and pseudo-second order kinetic models. These results can open a new avenue for the manufacturing of fibers with enhanced removal capacities for hexavalent chromium.

scholarly journals The interaction of spermine and pentamines with DNA

1987 ◽  
Vol 244 (1) ◽  
pp. 243-246 ◽  
Author(s):  
H S Basu ◽  
L J Marton
Keyword(s):  
High Temperature ◽  
Melting Temperature ◽  
Conformational Changes ◽  
Thermus Thermophilus ◽  
Total Charge ◽  
Amino Groups ◽  
Carbon Chains ◽  
Naturally Occurring ◽  
Calf Thymus

We studied the effects of spermine, two naturally-occurring pentamines isolated from the thermophile Thermus thermophilus and one synthetic pentamine on the aggregation and ‘melting’ temperature of calf-thymus DNA and on the B-to-Z transition of poly(dG-me5dC). All pentamines caused aggregation of DNA at much lower concentrations than that of spermine. Concentrations that increased the melting temperature of DNA and induced the B-to-Z transition in poly(dG-me5dC) were different for each pentamine, but were comparable with the concentration of spermine needed to cause these effects. Our results suggest that both the total charge and the distance separating the charge, which is a function of the length of the carbon chains between amino groups, are important for the induction of conformational changes in DNA. The biological role of pentamines in T. thermophilus appears to be related to their ability to promote DNA condensation at high temperature.

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