Hemoglobin as a potential source of natural regulatory oligopeptides.

Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia. aaz@inbi.ras.ru

Theoretical structure-function analysis of all possible hemoglobin molecule fragments was performed to determine sites that could be potential sources of regulatory oligopeptides. Known data on bovine hemoglobin primary structure and information of the EROP-Moscow database concerning structure and functions of natural oligopeptides were used along with a computer program complex. A total of 6750 natural non-hemoglobin oligopeptides with hemoglobin fragments of 2-14 amino acid residues were found. Structures of 20 of them were completely identical to hemoglobin fragments. Most of the revealed oligopeptides exhibit properties of neuropeptides, antimicrobial agents, and hormones. A number of them exhibit functions previously not known for hemoglobin fragments. The possibility of natural formation of regulatory oligopeptides from hemoglobin and other food protein molecules, generation of the exogenous oligopeptide pool, their participation in regulation processes as well as accordance of results obtained here with the oligopeptide continuum concepts are discussed.

Porous nanosheet-based ZnO microspheres for the construction of direct electrochemical biosensors

Nanosheet-based ZnO microsphere with porous nanostructures was synthesized by a facile chemical bath deposition method followed by thermal treatment, which was explored for the construction of electrochemical biosensors. Spectroscopic and electrochemical researches revealed the ZnO-based composite was a biocompatible immobilization matrix for enzymes with good enzymatic stability and bioactivity. With advantages of nanostructured inorganic–organic hybrid materials, a pair of stable and well-defined quasi-reversible redox peaks of hemoglobin was obtained with a formal potential of −0.345 V (vs. Ag/AgCl) in pH 7.0 buffer. Facilitated direct electron transfer of the metalloenzymes with an apparent heterogeneous electron transfer rate constant (ks) of 3.2 s−1 was achieved on the ZnO-based enzyme electrode. Comparative studies demonstrated the nanosheet-based ZnO microspheres were more effective in facilitating the electron transfer of immobilized enzyme than solid ZnO microspheres, which may result from the unique nanostructures and larger surface area of the porous ZnO. The prepared biosensor displayed good performance for the detection of H2O2 and NaNO2 with a wide linear range of 1–410 and 10–2700 μM, respectively. The entrapped hemoglobin exhibits high peroxidase-like activity for the catalytic reduction of H2O2 with an apparent Michaelis-Menten constant of 143 μM. The nanosheet-based ZnO could be a promising matrix for the fabrication of direct electrochemical biosensors, and may find wide potential applications in biomedical detection and environmental analysis.
Xianbo Lua, Haijun Zhanga, Yuwen Nia, Qing Zhanga and Jiping Chen, a,

Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, PR China