Species, structure and proposed function of the heterogeneous, low-molecular-weight nuclear RNAs (sn RNA) (65-300 nucleotides) which are not directly involved in protein synthesis, are reviewed. The RNAs mainly contain two families of RNA: One has an unusual, trimethyl guanine (m32, 2, 7G) at the 5' end of molecule, some monomethylated bases and/or pseudouracil. The other family of RNAs of which 5' end is pppGp' has no modified bases. These RNAs appear to be the products by DNA-dependent RNA polymerase I or III. Several presumptive models are summarized, which are presented for regulation by snRNA of transcription, splicing and/or selection of mRNA on ribosomes based on snRNA-DNA and/or snRNA-gene transcripts interaction.
Possibilities that multiple circadian oscillators coexist within one individual organism are reviewed. The possibility has been suggested in two ways. One is cut-and-see experiments, in which the lesion of the putative structure in the central nervous system containing the driving oscillator has not always led to comlplete disappearance of the overt rhythm. The other is kinetic or functional analyses which resulted in finding of desynchronization, rhythm-splitting and some other phenomena suggestive of the existence of multiple oscillators. Under present circumstances, the concrete feature of hierarchy supposed to be made up of the oscillators is quite unknown, although some speculations for it have been presented. Methodological apd technical problems pertaining to the rhythm study are also discussed.
Recent studies of quantum chemical calculations on visual pigments are summerized. It is generally accepted that the red-shift and the wide distribution of λmax's (wavelengths of absorption maximum) of visual pigments can be explained by the protonated Schiff-base binding of retinal with opsin and by the electrostatic interaction between retinal and a counter-ion on opsin. Experimental and theoretical evidences for this primary linkage and interaction are first presented and discussed. Secondly, recent studies of the secondary in teractions between retinal and opsin are summarized. At present, the following three types of the secondary interactions are mainly investigated: (1) the interaction of retinal through itsβ-ionone ring; (2) the interaction through its 9-methyl group; (3) the interaction with the local electric field due to the microenvironment of chromophore. Thirdly, as for the photochemical conversion of rhodopsin to bathorhodopsin, it is generally considered that retinal isomerizes from 11-cis to all-trans form. Concerning to the mechanism of this isomerization, the potential surfaces of the ground and excited states have recently been examined by several authors. Their models for the intermediates in photobleaching process are reviewed and discussed briefly.
The stability of the adsorbed monolayer, black lipid membrane (BLM) and bilayer vesicles is analysed by the use of the statistical mechanics. It is emphasized the effect of the concentration of the constitutive molecules of the membranes in the solutions on the stability of them. The BLM is shown to be in a metastable supersaturated liquid state for an appropriate condition. The bilayer vesicles are shown to be stable above the concentration at which the interfacial tension of the BLM diminishes to zero.