Magnesium complexes biology

Porphyrins and their derivatives play critical roles in many biological functions. Some of the most remarkable examples are protoporphyrin IX and its iron complex that constitutes the heme prosthetic group, and the magnesium complexes of pheophytin a and bacteriopheophytin a that are known as chlorophyll a and bacteriochlorophyll a, respectively. These natural compounds are illustrated in Fig. 1 together with the structure of porphin,... 

When the requirement is for many routine analyses of sodium and potassium, a simple filter fiame photometer burning a low temperature flame should be purchased. Many such models are on the market. On the other hand, if analysis for calcium and magnesium in biological fluids is also required, then only a fairly complex instrument with monochromator, photomultiplier, and high-temperature flame is satisfactory (Fig. 4). Compromise instruments between these two extremes lose the simplicity of the first type without gaining the versatility of the second. 

Our knowledge of the stereochemistry of porphyrins and related tetrapyrrole macrocycles has expanded rapidly since the first reported x-ray structure determination in 1959 The structures of metallotetrapyrrole complexes are of interest because of the common occurrence of this type of macrocycle in biological systems. As is well known, foremost among these are the heme proteins (iron derivatives), the various photosynthetic pigments (magnesium complexes), the vitamin Bn coenzyme (cobalt corrinoids), and coenzyme F430 (nickel corphinoids) of the methanogenic bacteria. 

You have probably noticed the negative charge on both ATP and ADP. This is conterbalanced in these, and other phosphate-containing biological molecules (e.g. DNA) by cations, usually Mg2+, in fact, both ATP and DNA may be regarded as magnesium complexes. 

The natural fluorescence of CTC and its derivatives has been used extensively to determine small amounts of CTC in biological materials. Kohn (86) showed that the fluorescent complex formed by CTC with calcium ions and barbital could be extracted from animal tissues into an organic solvent and then measured spectrofluorometrically. The intense fluorescence of anhydro-CTC was used by Hayes and DuBuy (87) to determine CTC in animal tissues, tissue culture cells, and bacteria. Poiger and Schlatter (88) extracted CTC from biological material into ethyl acetate as the CTC-calcium trichloroacetate ion pair. The fluorescence of the antibiotic was then enhanced by the addition of magnesium ions and a base. 

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