Solubility haemoglobin

In section 5.2.3 we discussed the effect of salts on the solubility of organic electrolytes. The parabolic effects of salts on protein solubility (Fig. 11.6) might, at first sight, seem unexpected. Data, produced over 70 years ago, on haemoglobin solubility (Fig. 11.6b) shows a general increase in solubility with increasing ionic strength of salts such as NaCl, KCl and... 

The time-scale of this haem conversion is related to the antioxidant status of the LDL and that of the erythrocyte lysate. The incorporation of lipid-soluble antioxidants, such as tocopherol and butylated hydroxy-toluene (BHT) at specific time points during the LDL-erythrocyte interaction, prolongs the lag phase to oxidation, eliminates the oxy to ferryl conversion of the haemoglobin and delays the oxidative modification of the LDL. 

Q. Lu, S.S. Hu, D.W. Pang, and Z.K. He, Direct electrochemistry and electrocatalysis with haemoglobin in water-soluble quantum dots film on glassy carbon electrode. Chem. Commun. 20, 2584—2585 (2005). 

The presence of lead and hexavalent chromium in these products is of chronic hazard concern and the EU has classified these pigments as harmful substances. Lead is soluble at stomach-acid concentrations and can accumulate in the organism. The results of a high lead intake include inactivation of enzymes and disturbances in the synthesis of haemoglobin. Hexavalent chromium compounds are considered to be carcinogenic. For these reasons the usage of lead chromate pigments has declined considerably in recent years. 

Finally the solubility of reduced haemoglobin is different from that of oxyhaemoglobin and in general the two forms crystallize in different space groups (6, 34, 35). 

Oxygen is essential for human life as each cell requires a constant supply to stay alive. Our bodies depend upon three main carriers of oxygen from the outside air into the cell processes. Oxygen gas is not very soluble in water and equally poorly soluble in the blood and body fluids. For example, one litre of blood only carries 2.7 ml of oxygen. This would be totally inadequate to support life. Arterial blood carries 2.7 ml O2 per litre of blood dissolved in it and 204.7 ml chemically combined with haemoglobin. 

Q4 The water-soluble vitamins (B and C) and essential minerals, such as iron, are absorbed in the small intestine. The reabsorption of iron in the duodenum and proximal jejunum involves a complex active transport process. When there is a large reduction in the surface area of this part of the gut, there is a marked reduction in reabsorption of iron (and B vitamins). Haemoglobin synthesis is decreased, leading to development of anaemia, which is a common symptom in celiac disease. 

Histones are small and stable basic proteins and contain fairly large amounts of basic amino acid, histidine. They are soluble in water, but insoluble in ammonium hydroxide. They are not readily coagulated by heat. They occur in globin of haemoglobin and nucleoproteins. 

Rguie 11.6 (a) A generic plot of log(solubilily) os a function of square root of ionic strength (/ ) for proteins, (b) The plot for haemoglobin at 25°C, indicating the influence of the nature of the salt. Solubility is expressed as grams per 1000 grams H2O. 

Ammonium sulphate is commonly used as a precipitant because of its great solubility and ready availability. It can liberate ammonia, which reacts with heavy atom derivatives. This problem can in some circumstances be alleviated by changing the mother liquor of the crystals to phosphate. Ammonium sulphate caused further problems in the analysis of the crystal structure of oxyhaemoglobin. In the presence of this salt and under irradiation, crystals of oxyhaemoglobin were oxidised rapidly to aqua-met-haemoglobin. The problem was solved by growing the crystals under usual conditions [34] and then transferring them to 3 M phosphate [16]. 

Soluble guanylate cyclase is activated by nitric oxide (NO) (see Section 3.4). NO has been implicated in the generation of long term depression (LTD) of parallel fiber-mediated EPSP s in Purkinje cells. LTD can be prevented by the application of haemoglobin that absorbs NO, or by the inhibition of NO synthesis (Crepel and Jaillard, 1990 Shibuki and Okada, 1991 Ito, 1991). However, nitric oxide synthase, the synthesizing enzyme of NO, appears to be absent from the Purkinje cell (Section 3.4.). 

Finally, what of anaemia This, too, is a symptom of scurvy, but is not a physiological failure in the sense of those discussed above. In this case, vitamin C acts on the inorganic iron in food in the stomach and intestines, converting it from the insoluble form usually found in food (Fe3+) to the soluble form (Fe2+) that we can absorb in our intestines. (This is the reverse of the reaction that took place on a huge scale in the Pre-cambrian oceans, leading to the precipitation of insoluble iron into banded iron formations, discussed in Chapter 3). Without adequate supplies of vitamin C, we cannot absorb enough iron to stock red blood cells with haemoglobin (which contains iron), and so we develop anaemia. 

Bilirubin is derived from the tetrapyrrole prttsthetic group found in haemoglobin and the cytochromes. It is normally conjugated with glucuronic acid to make it more soluble, and excreted in the bile (Fig. 2). There are three main reasons why bilirubin levels in the blood may rise (Fig.. ) ... 

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