The physiological function of myoglobin is reviewed briefly with the emphasis of the "oxygen buffer" and facilitation of oxygen diffusion.
The techniques, employed by authors, for persuing the absorption changes of myoglobin and cytochrome aa₃ with the hemoglobin-free perfused rat heat are presented, where the oxygenation-deoxygenation of myoglobin and redox-change of cytochrome aa3 are successfully measured with the millisecond time-range during the 1 cycle of contraction-relaxation. From the detailed analysis of the absorption change of both components during the each heat beat, it is concluded that myoglobin in the cardiac tissue acts as oxygen buffer to iron out the fluctuation of intracellular oxygen concentration arising from the contraction-relaxation cycle.

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The larger ribosomal subunit from all organisms examined to date has been found to contain one RNA molecule with a molecular weight of 40, 000, the socalled "5S RNA". The primary structures of 5S RNAs from more than ten species have been determined so far. A large number of models for their secondary structure have been proposed on the basis of many experimental and theoretical studies. However, little is known about the real function of 5S RNA in ribosome structure at the presnet time.
In this article, recent studies on primary and secondary structure of 5S RNA are briefly reviewed and several secondary structure models, including ours, are compared with each other. Some of the possible functions of 5S RNA expected from our secondary structure model are also discussed.

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There are several regulatory proteins other than well-known troponin and tropomyosin in muscle. These are small in contents, but play a role mainly in regulating ordered structure of muscle. The proteins locating in the A band of myofibril are M-protein, C-protein, γ-component and J-protein. Those in I band are actinins, β, γ-, and 10S. α-Actinin is a Z-line substance. In this review the nature and function of these minor regulatory proteins are critically reviewed.

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A brief survey of recent advances in physical and biochemical studies on the structure of low density lipoprotein is made with approximately 20 literatures of immediate interest to the author. The distribution of lipids and proteins in the lipoprotein particle is discussed as a major concern at the present stage of investigation which is still very infantile despite the continued effort of many researchers around the world. The presence of the protein rich shell over the hydrocarbon rich core in the lipoprotein particle has been convincingly proposed by several workers including the present author. The conformation of apo-LDL and the distribution of different lipids in the lipoprotein particle are two of several major problems in this field that await vigorous investigations.

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