Proteins semiconductivity

The origins, principles, methods, and modes of capillary electrophoresis (CE) are discussed. Massive application of electrophoresis methods started after Tiselius s moving boundary method that was optimized by the use of paper or a gel as a semiconducting medium. The applications of paper and gel electrophoresis were situated mostly in the biochemical environment for the analysis of proteins, amino... 

Eley DD, Spivey DI (1960) The semiconductivity of organic substances. Part 6. A range of proteins. Trans Faraday Soc 56 1432-1442... 

Any search for polymer products on the internet will reveal the staggering number and variety of materials now available. It would seem that every type of polymer imaginable for just about any possible application already exists. Yet research in polymer science is among the most active in any held of chemistry. Today researchers are still inventing many new kinds of polymers with a host of specialized properties and uses. Some of the most exciting research involves the development of conductive and semiconductive polymers, den-drimers, and synthetic proteins. 

Similarly, Cherukuri et al. used the near-IR fluorescence of individualized semiconducting SWNTs to study their blood elimination kinetics and biodistribution in rabbits.127 The pluronic copolymer-coated SWNTs were intravenously administered into rabbits at a dose of 20 pg S WNT per kilogram of body mass. The pluronic coating was found to be displaced by blood protein within seconds, as indicated by changes in the near-IR emission spectra. The nanotube concentration in the blood semm decreased exponentially with a half-life of 1 h, and no adverse effects were observed in terms of the rabbit behavior and the pathological examination. At 24 h post administration, significant concentrations of nanotubes were found only in the liver.127... 

The Hartree-Fock gap for the main chain is 12.4 eV (which decreases to 11.6 eV due to the long-range correlation), while for the hydrogen-bonded chain its value is (due to the smaller bandwidths) still larger ( 14.8 eV). Owing to this large gap intrinsic semiconduction in proteins seems to be negligible and the role of various impurities becomes important.99... 

Fig. 10.3-16(b) [69]. After amide bond formation, these proteins can be further modified using commercially available avidin derivatives, including those bearing fluorescent semiconducting nanocrystals [70], As the recognition sequence appears with little or no frequency in the proteome of most cells, virtually absolute selectivity can be obtained. 

H. Cardew and the author (67) have found the semiconductivity energy gap of haemoglobin to be much greater than for macrocyclic aromatic substances. Thus, mesomeric paths in proteins are probably limited to the immediate neighborhood of the active site, and in this respect proteins probably differ from semiconducting oxide catalysts (68). The effects of hydration are still to be examined, but it seems likely that this will effect mainly the surface of the protein molecule. 

B. Rosenberg, Electrical Conductivity of Proteins II Semiconduction in Crystalline Bovine Hemoglobin, J. Chem. Phys. 36, 816 (1962) B. Rosenberg and H. C. Pant, The Semiconducting Rectifier Behavior of a Bimolecular Lipid Membrane, Chem. Phys. Lipids 4, 203 (1970) Electrochemistry on a Bimolecular Lipid Membrane, ibid. 6, 39... 

B. Rosenberg, Electrical Conductivity of Proteins. II. Semiconduction in Crystalline Bovine Hemoglobin, J. Chem. Phys. 36, 816 (1962). 

The structure of proteins (and their constituents) and the problem of semiconductivity in biopolymers... 

The third, and to some extent the most interesting type of study carried out in relation to proteins is concerned with an aspect of their supramolecular structure, namely the occurrence of electronic semiconductivity owing to an overall electronic delocalization through the whole polymer resulting in the formation of energy bands. 

The conclusion to be drawn from these results is that inasmuch as polypeptides can be accommodated by the proposed model, pure proteins should be rather quite good insulators. The observed semiconductivity, which, following the quoted work of Eley, Rosenberg and collaborators, involves an energy gap of 2-3 eV, is probably extrinsic, originating from extra energy levels, due to the presence of defects or impurities. 

The problem of semiconductive properties is not peculiar to proteins but concerns also other types of biological macromolecules, in particular the nucleic acids. Semiconductivity, with an energy gap for dry DNA of about 2.4 eV has been observed by a number of authors . It has been investigated theoretically from the standpoint of the possible existence of... 

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