Proteins hypochromicity

Whereas proteins have their low energy absorption band at 280 nm, polynucleotides typically have maxima at 260 nm (38,500 cm ). A phenomenon of particular importance in the study of nucleic acids is the hypochromic effect. In a denatured polynucleotide the absorption is approximately the sum of that of the individual components. However, when a double helical structure is formed and the bases are stacked together, there is as much as a 34% depression in the absorbance at 260 nm. This provides the basis for optical measurement of DNA melting curves (Fig. 5-45).45,86 The physical basis for the hypochromic effect is found in dipole-dipole interactions between the closely stacked base pairs.7,86,87... 

Hypoproteinemia may result in low levels of serum calcium, ceruloplasmin, and transferrin. Because losses of iron are at most 0.5-1.0 mg/24 hr, even with the heaviest proteinuria, other factors must operate to produce iron deficiency and microcytic hypochromic anemia. Although the copper-binding protein ceruloplasmin is lost in the urine in nephrotic subjects and its plasma levels are low, plasma and red cell copper concentrations are usually normal. Zinc circulates mainly bound to albumin and also to transferrin, and thus the reported reduction zinc concentration in plasma, hair, and white cells in nephrotic patients is not surprising. 

Iron is stored in intestinal mucosal cells as ferritin (an iron/protein complex) until needed by the body. Iron deficiency results from acute or chronic blood loss, from insufficient intake during periods of accelerated growth in children, or in heavily menstruating or pregnant women. Therefore it essentially results from a negative iron balance due to depletion of iron stores and inadequate intake, culminating in hypochromic microcytic anemia. Supplementation with ferrous sulfate is required to correct the deficiency. Gastrointestinal disturbances caused by local irritation are the most common adverse effects caused by iron supplements. 

Partial Helical Content of Proteins in Aqueous Solution Estimated from Hypochromism of Peptide Bond Absorption Near 190 mp ... 

Harris et al. (H4) reported a case of an adult patient with hematological abnormalities unresponsive to the usual hematopoietic agents and characterized by a hypochromic anemia, leucocytosis, high serum iron, and high percent iron-binding protein saturation. Measurements of the urinary excretion of kynurenine, kynurenic acid, acetylkynurenine, xanthurenic acid, o-aminohippuric acid before and after an oral dose of 4 g L-tryptophan indicated abnormalities of tryptophan metabolism. This alteration was partially normalized on a 1-mg pyridoxine dose and completely normalized at the 10-mg level. Also the clinical and laboratory abnormalities disappeared and hematological remission followed the pyridoxine administration. 

Decreased Plasma Levels. Transferrin is a negative APR the most common cause of low levels is inflammation or malignancy. Decreased synthesis is seen with chronic liver disease and malnutrition (see Chapter 47). Protein loss, as in the nephrotic syndrome or protein-losing enteropathies, also results in low levels. In hereditary atrans-ferrinemia, a very low level of Tf is accompanied by iron overload but severe hypochromic anemia resistant to iron therapy. 

Both the hematocrit values and the red cell counts (A) show much the same story. When these values were used to compute the mean corpuscular hemoglobin concentration (Figure 3) and the mean cell volumes (Figure 4) it was found that indeed a microcytic hypochromic anemia had been produced at the lowest iron intake levels.- However, the effect was much more pronounced when 20% protein was fed than when the diet contained 10% casein. 

In the initial phase of depletion of the iron content of the body, the iron stores maintain normal levels of hemoglobin and of other iron proteins. With exhaustion of storage iron, hypochromic and microcytic anemia becomes manifest. 

The internal structure of the cross-linked synthetic polypeptides is maintained by heat-stable, covalent bonding between the cross-linked amino acid side chains and by heat-labile, noncovalent side chain interactions between glutamic acid and lysine residues (electrostatic) and between tyrosine residues (nonpolar). The stability of the spatial structure of a polymer depends upon the relative proportion of covalent and noncovalent bonding that it contains and increases as the number of cross-links increases. According to the current theories of protein structure, the charged amino acid residues would be arrayed on the surface of the molecule, and the tyrosine residues would be internally placed and thus interact to give a hypochromic effect. Am(6)-poly Glu52Lys33Tyr15 (No. 3B) (Fr. 1) displays such an effect, and the molar extinction coefficient of the cross-linked derivative is 25% lower than that of the parent polymer. This hypo-... 

A. Iron and Vitamin Deficiency Anemias Microcytic hypochromic anemia, caused by iron deficiency, is the most common type of anemia. Megaloblastic anemias are caused by a deficiency of vitamin B, or folic acid, cofactors required for the normal maturation of red blood cells. Pernicious anemia, the most common type of vitamin Bj, deficiency anemia, is caused by a defect in the synthesis of intrinsic factor, a protein required for efficient absorption of dietary vitamin B 2, or by surgical removal of that part of the stomach that secretes intrinsic factor. 

Negative acute-phase reactant Chronic inflammation Malnutrition Chronic liver diseases Protein-losing syndromes Iron overload Congenital defect atransferrinemia (severe hypochromic anemia)... 

Patients suffering from renal failure and receiving dialysis treatment frequently suffer from a normocytic anemia successfully treated with human recombinant erythropoietin, a regulatory protein synthesized by the kidney. However, patients often also exhibit a microcytic, hypochromic anemia that can be separated from the normocytic anemia of renal insufficiency, and that is refractory to erythropoietin (Rosenlof et al. 1990). Al administration to animals produces a similar microcytic anemia (Touam et al. 1983 Fulton and Jeffery 1993). In addition, not only can the anemia be reversed by desferrioxamine treatment (Tielmans et al. 1985), but a prospective clinical study correlated plasma Al levels with severity of the anemia (Short et al. 1980). Patients undergoing hemodialysis with Al-contaminated fluids showed an increased plasma Al and decreased hematocrit both parameters were then reversed when the patients were switched to an Al-free dialysate. 

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