ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The aromatic residues such as tryptophan (Trp) and tyrosine (Tyr) in human adult hemoglobin (Hb A) are known to contribute to near-UV circular dichroism (CD) and UV resonance Raman (RR) spectral changes upon the R → T quaternary structure transition. In Hb A, there are three Trp residues per αβ dimer: at α14, β15, and β37. To evaluate their individual contributions to the R → T spectral changes, we produced three mutant hemoglobins in E. coli; rHb (α14Trp→Leu), rHb (β15Trp→Leu), and rHb (β37Trp→His). Near-UV CD and UVRR spectra of these mutant Hbs were compared with those of Hb A under solvent conditions where mutant rHbs exhibited significant cooperativity in oxygen binding. Near-UV CD and UVRR spectra for individual Trp residues were extracted by the difference calculations between Hb A and the mutants. α14 and β15Trp exhibited negative CD bands in both oxy- and deoxy-Hb A, whereas β37Trp showed positive CD bands in oxy-Hb A but decreased intensity in deoxy-form. These differences in CD spectra among the three Trp residues in Hb A were ascribed to surrounding hydrophobicity by examining the spectral changes of a model compound of Trp, N-acetyl-l-Trp ethyl ester, in various solvents. Intensity enhancement of Trp UVRR bands upon the R → T transition was ascribed mostly to the hydrogen-bond formation of β37Trp in deoxy-Hb A because similar UVRR spectral changes were detected with N-acetyl-l-Trp ethyl ester upon addition of a hydrogen-bond acceptor.

Zinc/platinum (Zn/Pt) bimetallic micromotors have been developed. They moved based on the reduction of fuel compounds such as bromine, p-benzoquinone, and methanol at the surface of the Pt and the oxidation (dissolution) of Zn that occur simultaneously. The redox potential of Zn 2+ /Zn is very negative and was advantageous to cause the redox reactions. The motion of the motor and the reactions that occurred on the surface were investigated. With test motors containing Ni, it was revealed that the Zn/Pt motors showed almost unidirectional motion to the Zn side. Toxicity of Zn 2+ is relatively lower than that of other metal ions. Also, the motor features the use of mild compounds such as methanol that are not harmful to tissues or organisms as their fuels.

Reaction of C60-substituted benzotetrasilacyclohexene (3) and bromine gives rise to the 6,7:8,9-dibenzo-3-oxo-1,2,2,4,4,5-hexaphenyl-1,2,4,5-tetrasilabicyclo[3.2.2]nonadiene (5) and C60. Intramolecular cyclization of a silyl radical intermediate is proposed to account for the obtained products.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.