Hemoglobins acidity

Figure 2-1 S3. The ViewerLite shows an elaborate depiction of hemoglobin on the right-hand side, with the amino acids in a cascade window on the left.

Fig. 5. Chloiide shift where KHb is potassium hemoglobin and HHb is acid hemoglobin (16).

Proteins may consist exclusively of a polymeric chain of amino acids these are the simple proteins. Quite often some other chemical component is covalendy bonded to the amino acid chain. Glycoproteins and Hpoproteins contain sugar and Hpid components, respectively. Porphyrins are frequently associated with proteins, eg, in hemoglobin. Proteins bound to other chemical components are called conjugated proteins. Most enzymes are conjugated proteins. 

C rb myl tion. Modification of the amino-terminal groups of hemoglobin (Hb) by the carbamylation reaction using isocyanic acid [75-13-8]... 

CPR can be used to find continuous paths for complex transitions that might have hundreds of saddle points and need to be described by thousands of path points. Examples of such transitions include the quaternary transition between the R and T states of hemoglobin [57] and the reorganization of the retinoic acid receptor upon substrate entry [58]. Because CPR yields the exact saddle points as part of the path, it can also be used in conjunction with nonnal mode analysis to estimate the vibrational entropy of activation... 

Lesk and Chothia did find, however, that there is a striking preferential conservation of the hydrophobic character of the amino acids at the 59 buried positions, but that no such conservation occurs at positions exposed on the surface of the molecule. With a few exceptions on the surface, hydrophobic residues have replaced hydrophilic ones and vice versa. However, the case of sickle-cell hemoglobin, which is described below, shows that a charge balance must be preserved to avoid hydrophobic patches on the surface. In summary, the evolutionary divergence of these nine globins has been constrained primarily by an almost absolute conservation of the hydro-phobicity of the residues buried in the helix-to-helix and helix-to-heme contacts. 

Sickle-cell anemia is the classic example of an inherited disease that is caused by a change in a protein s amino acid sequence. Linus Pauling proposed in 1949 that it was caused by a defect in the hemoglobin molecule he thus coined the term molecular disease. Seven years later Vernon Ingram showed that the disease was caused by a single mutation, a change in residue 6 of the P chain of hemoglobin from Glu to Val. 

FIGURE 5.13 Two basic types of biological transport are (a) transport within or between different cells or tissues and (b) transport into or out of cells. Proteins function in both of these phenomena. For example, the protein hemoglobin transports oxygen from the lungs to actively respiring tissues. Transport proteins of the other type are localized in cellular membranes, where they function in the uptake of specific nutrients, such as glucose (shown here) and amino acids, or the export of metabolites and waste products. 

As noted, hemoglobin is an tetramer. Each of the four subunits has a conformation virtually identical to that of myoglobin. Two different types of subunits, a and /3, are necessary to achieve cooperative Oa-binding by Hb. The /3-chain at 146 amino acid residues is shorter than the myoglobin chain (153 residues), mainly because its final helical segment (the H helix) is shorter. The a-chain (141 residues) also has a shortened H helix and lacks the D helix as well (Figure 15.28). Max Perutz, who has devoted his life to elucidating the atomic structure of Hb, noted very early in his studies that the molecule was... 

A model for the allosteric behavior of hemoglobin is based on recent observations that oxygen is accessible only to the heme groups of the a-chains when hemoglobin is in the T conformational state. Perutz has pointed out that the heme environment of /3-chains in the T state is virtually inaccessible because of steric hindrance by amino acid residues in the E helix. This hindrance dis-... 

Blut rot, n. hemoglobin hematin, ruhr, /. dysentery. s ure, /, thiocyanic acid. 06s, scheibe, /. blood corpuscle. schlag, m. apoplexy. seuche, /. anthrax. stein, m. bloodstone, hematite. 

The amino acid sequence in hemoglobin, with 574 units, is known. 

Alpert has shown [47] that poly(succinimide)-silica can be further hydrolyzed to poly (aspartic acid)-silica or condensed with [3-alanine in aqueous solution to form a covalently bonded copolymer of 2-carboxyethyl aspartamide and aspartic acid. The content of carboxyl groups generated by this way has not been quantified directly, but the cation-exchange hemoglobin capacity has been measured for a series of the packings. Thus, the optimal concentration of poly(succinimide) used in the synthesis was found to be 2 5%. 

Much research focuses on the structures, properties, and uses of the complexes formed between d-metal ions acting as Lewis acids and a variety of Lewis bases, partly because they participate in many biological reactions. Hemoglobin and vitamin B12, for example, are both complexes—the former of iron and the latter of cobalt (Box 16.1). Complexes of the d-metals are often brightly colored and magnetic and are used in chemistry for analysis, to dissolve ions (Section 11.13), in the... 

The primary structure of a protein is the sequence of residues in the peptide chain. Aspartame consists of phenylalanine (Phe) and aspartic acid (Asp), and so its primary structure is Phe-Asp. Three fragments of the primary structure of human hemoglobin are... 

This series in heterocychc chemistry is being introduced to collectively make available critically and comprehensively reviewed hterature scattered in various journals as papers and review articles. All sorts of heterocyclic compounds originating from synthesis, natural products, marine products, insects, etc. will be covered. Several heterocyclic compounds play a significant role in maintaining life. Blood constituents hemoglobin and purines, as well as pyrimidines, are constituents of nucleic acid (DNA and RNA). Several amino acids, carbohydrates, vitamins, alkaloids, antibiotics, etc. are also heterocyclic compounds that are essential for life. Heterocyclic compounds are widely used in clinical practice as drugs, but all applications of heterocyclic medicines can not be discussed in detail. In addition to such applications, heterocyclic compounds also find several applications in the plastics industry, in photography as sensitizers and developers, and the in dye industry as dyes, etc. 

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