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Precise analysis using the denaturant gradient gel electrophoresis which was devised by Fischer and Lerman (Cell 16, 191-200, 1979), was found to present specific patterns of fine structures for double stranded DNA fragments. These seem to be a mobility change of DNA fragments caused by specific denaturation processes. The effect of denaturants on DNA melting was ascertained to be similar to the effect of temperature. The observed patterns, in comparison with the melting processes of DNAs theoretically obtained, were closely related to DNA meltings and strand dissociations. A number of electrophoretic mobility transitions showed the retardation correspondent to each of the cooperative meltings. Strand dissociations occurred under the conditions theoretically predicted. The degree of retardation in electrophoresis for DNA fragments seemed to correspond to the size of melted regions. Methods presented here were proved to have advantages over the conventional ones for the study of DNA stability maps.

A bacteriophage is continuously cultured in the flow of the host bacterial cell under the control of a minicomputer. In the culture, the population of the noninfected cell is kept constant by the endogeneous regulation mechanism, so it is called the ’’cellstat’’ culture. Due to the high dilution rate of the host cell, the mutant cell cannot be selected in the cellstat. Therefore, the cellstat is suitable for the study of the mutation rate and the selection process of a bacteriophage under well‐defined environmental conditions (including physiological condition of the host cell) without being interfered by host‐cell mutations. Applications to coliphage fd, a secretion type phage, are shown as a measurement example. A chimera between fd and a plasmid pBR322 is cultured more than 100 h. The process of population changeovers by deletion mutants indicates that the deletion hot spots exist in this cloning vector and that this apparatus can be used also for testing instability of a recombinant DNA.

The initial rate and the aging effect of ethylene polymerization with TiCl4- and TiCl3-AlEt3 catalyst were investigated. The initial rate, r, was expressed by the equation; r=k1PE+k2PE2, where pE is the ethylene partial pressure and where k1 and k2 are constants. The explanation of the equation is as follows:&(active site)+M\xrightarrowk_1(polymerization site), rate, k_1P_E&(polymerization site)+M^*\xrightarrowk_2(propagation), rate, k_2P_E^2M shows the ethylene monomer which is liberated by the catalyst formation or which is introduced into the system. M* is the monomer which is introduced into the system. The initial rate decreased in the TiCl4-AlEt3 system with the aging-time interval; on the other hand, in the TiCl3-AlEt3 system the rate showed its maximum at about half an hour’s aging. The optimum aging temperature was found to be 20°C. The decrease in the rates between the two systems may be ascribed to the reduction of the Ti atom in the initial valence state of the reaction to the lower valence.

Restriction endonucleases (13 out of 18 species used for the test) were certified to cleave single-stranded(ss)DNA. Such enzymes as AvaII, HaeII, DdeI, AluI, Sau3AI, AccII,TthHB8I and HapII were newly reported to cleave ssDNA. A model to account for the cleavage of ssDNA by restriction enzymes was proposed with supportive data. The essential part of the model was that restriction enzymes preferentially cleave transiently formed secondary structures (called canonical structures) in ssDNA composed of two recognition sequences with two fold rotational symmetry. This means that a restriction enzyme can cleave ssDNAs in general so far as the DNAs have the sequences of restriction sites for the enzyme, and that the rate of cleavage depends on the stabilities of canonical structures.

Decaborane formed adducts with cyclohexanones, 2-octanone, acetaldehyde, or acetone, which were cleft in the presence of water into alcohols, boric acid, and hydrogen. Olefins and boroxins as secondary products were identified.

The catalytic hydroboration of ethylene with diborane to triethylborane in the gas phase was studied in the presence of various catalysts. The acidity of catalysts and the reaction activity were measured; the increase in the activity can be related to surface acidity of the catalysts.

Decaborane formed adducts with cyclohexanones, 2-octanone, acetaldehyde, or acetone, which were cleft in the presence of water into alcohols, boric acid, and hydrogen. Olefins and boroxins as secondary products were identified.

The catalytic hydroboration of ethylene with diborane to triethylborane in the gas phase was studied in the presence of various catalysts. The acidity of catalysts and the reaction activity were measured; the increase in the activity can be related to surface acidity of the catalysts.