Mechanics of Biologies

Most of the terms, concepts, and equations for studying the mechanical properties of biological materials have already been developed in the previous sections of this 

Tissue Maximum Strength (MPa) Maximum Strain (%) Elastic Modulus (MPa) 

Source F. H. Silver and D. L. Christiansen, Biomaterials Science and Biocompatibility. Copyright 1999 by Springer-Verlag. 

The directional dependence of the mechanical properties of skin was first observed by Langer in 1861. C. R. von E. Langer (1819-1887), an Austrian anatomist, pierced small circular holes in the skin of cadavers and observed that these holes became elliptical with time. By joining the long axes of the ellipses, he produced a series of lines that subsequently were named after him. It is well known to surgeons that incisions made along the direction of Ranger s lines close and heal more rapidly. 

Although the proteins in skin are also composed of about 5% elastic fibers, they do not appear to affect the mechanical properties of the tissue. The elastic fibers are believed to contribute to the recoil of the skin, which gives it the ability to be wrinkle-free when external loads are removed. As humans age, the elastic fiber network of the skin is lost, and wrinkles begin to appear. The mechanical role of the elastic fibers is very different in vascular tissue, however. 

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Ravindranath and co-workers studied the electrochemical behavior of 5-amino-2-phenyl-4-arylazo-l,2-dihydro-3//-pyrazol-3-one (90UC864) and 5-methyl-4-arylazo-2-(pyridin-2-ylcarbonyl)-2,4-dihydro-3//-pyrazol-3-(Mie (90IJC895). Similar studies were undertaken by Jain and Damodharan of pyrazol-3-ones 408a-f (95CJC176) (Scheme 94). The underlying rationale for this study on the electrochemical reduction of these biologically important pyrazol-3-ones is that it can lead to information on the reaction routes and mechanisms of biological redox reactions. 

Figure 19.15 Mechanism of biological aldehyde and ketone reductions by the coenzyme NADH.

Non-enzvmatic simulation of nitrogenase reactions and the mechanism of biological nitrogen fixation. G. N. Schrauzer, Angew. Chem., Int. Ed. Engl., 1975, 14, 514-522 (36). 

Mechanisms of biological ion transport-carriers, channels and pumps in artificial lipid membranes. P. Lauger, Angew. Chem.,Int. Ed. Engl., 1985, 24, 905 (265). 

Exanrple Ester ( 2) was needed as a model compound to study mechanisms of biological ester hydrolysis. It is clearly made from acid (33) which could be made from aldehyde (34) by a Wittig reaction. We discussed the synthesis of (3b) on page 21. 

Schulz, G. E. (1979). In Molecular Mechanism of Biological Recognition (M. Balaban, ed.), pp. 79-94. Elsevier/North-Holland Biomedical Press, New York. 

In the case of the methylated xanthines, particularly theophylline, theobromine and caffeine, the preponderance of data on the metabolism of these compounds in man suggests that a methylated uric acid is the principal product. However, the data presented earlier proposes at best a 77 per cent accounting of the methylated xanthine administered. The question can be raised as to whether the final products observed upon electrochemical oxidation of these compounds aids these studies. Very recently studies of metabolism of caffeine have revealed that 3,6,8-trimethylallantoin is a metabolite of caffeine 48>. This methylated allantoin is, of course, a major product observed electrochemically. The mechanism developed for the electrochemical oxidation seems to nicely rationalize the observed products and electrochemical behavior. The mechanism of biological oxidation could well be very similar, although insufficient work has yet been performed to come to any definite conclusions. There is however, one major difference between the electrochemical and biological reactions which is concerned with the fact that in the former situation no demethylation occurs whereas in the latter systems considerable demethylation appears to take place. 

Matzke, M. and Matzke, A.J.M. (2003). RNA extends its reach. Science, 301, 1060-1061 Mulkidjanian, A.Y., Cherepanar, D.A., Heberle, J. and Junge, W. (2005). Proton transfer dynamics at membrane/water interface and the mechanism of biological energy conversion. Biochem. (Moscow), 70, 251-256... 

Theoretically, according to the mechanism of biological azo dye reduction, the processes of biological decolorization are oxidation-reduction reactions, in which transfer of electrons match with the proton flow by the help of coenzymes, such as NADPH/NADP+ and NADH/NAD+. The oxidation-reduction potentials of the couples of NADPH/NADP+ and NADH/NAD+ are -324 and -320 mV, respectively [25, 46]. The least AGo value of the conversion NADPH/NADP+ and NADH/NAD+ is 44 kJ [47]. Therefore, —93 mV, which is obtained from (1), could be considered as a rough limited ORP value for ordinary primary electron donors of the third mechanism of biological azo dye reduction. This was demonstrated by the results of many researches (Table 1). Hence, the observed failure of cyanocobala-min [30] and ethyl viologen [48] to act as a mediator is most probably due to their too low Ed values 530 and —480 mV, respectively. 

Although data presented in the previous section illustrate the diversity of cycloaromatization reactions, most of the following discussion will concentrate on the Bergman cyclization - a reaction that has been studied intensively in recent decades due to its role in the mechanism of biological activity of natural anticancer antibiotics.8,9 We will take advantage of the large body of data produced by this... 

Knorr, D., Heinz, V., Angersbach, A., and Lee, D.-U. 2002. Membrane permeabilization and inactivation mechanisms of biological systems by emerging technologies. In Engineering and Food for the 21st Century (J. Welti-Chanes, G.V. Barbosa-Canovas, and J.M. Aguilera, eds), pp. 699-713. CRC Press, Boca Raton, FL. 

Sirotkin AK, Zarubaev W, Poznyiakova LN et al. (2006) Pristine fullerene C60 different water soluble forms - different mechanisms of biological action. Full Nanotubes Carb Nanostruct. 43 327-333. 

Study of the operational mechanism of biological systems, particularly those of the living brain, and the use of these results in the redesign of computer software and hardware architecture based on semiconductor technology (Section 1.2). 

Mechanisms of Biological Oxidation and Implications for Multi-Enzyme Biocatalysis... 

The mechanism of biological action of 281 has been thoroughly investigated (04MI4, 04MI5). These 2-aminochromenes reveal anticancer activity as the result of caspase activation, and, consequently, starting the apoptosis mechanism. However, somewhat different 2-amino-4H-chromenes 161 show antitumor activity by another mechanism, which involves inactivation of antiapoptotic proteins of the Bcl-2 series. 

Pyranopyridines 179 and pyranoquinolines 185 are close to chromenes 281 in their mechanism of biological action. Compounds 179 and 185 at micro- and nanomolar concentrations (for the most studied compounds GI50 was about 3-3000 nM) cause arrest of cells in the G2/M phase and inhibit tubuline polymerization (07BML3872, 08JME2561). 

Diffusion The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space a major mechanism of biological transport, [nih]... 

Data on the photon energy dependence of the biological effect has been accumulated fairly well with strand-break induction in plasmid DNA, and with an inactivation of the spore of a bacterium. These studies gave us many clues to understand the induction mechanism of biological effects in cells. However, for a complete understanding, research in the following areas should be highly promoted. 

Lugovskoy SP, Legkostup LA (2002) Mechanism of biological action of lead on digestive system. Sovremennye Problemy Toksikologii (Russian Modern Problems of Toxicology ) 2 45-50... 

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