Bulletin Number Four 1985

roles, as structural elements and as chemical machines operating in a molecular level. A protein is a linear polymer o f amino acids, but is special in that each individual protein molecule has a unique three dimen sional structure which is intimately related to its functional properties. The biophysical research on proteins in the Physics Department is concentrated on the two areas described below, and the researchers include Drs. K.C. Cho, C.L . Choy, W.P. Leung and C.M. Che (Chemistry Department, University o f Hong Kong). (1) An important but d ifficu lt biophysical problem is how the protein becomes folded once syn­ thesized in the body, and how is this folded structure maintained. Using myoglobin (the protein responsible for oxygen transport in the muscle) as a model system, we have observed by transient optical study that the folding and unfolding processes do not take place in one step, but involve a number o f intermediates. The equilibrium studies have contributed to the understanding o f the relative importance o f various effects, including pH, hydrophobic and electrostatic interactions, in stabilizing the protein structure. In addition to the static structure, dy­ namic properties such as the flexib ility o f the entire molecule are also o f significance in protein functions. For example, it is through structural fluctuations that oxygen molecules are able to diffuse into the interior o fmyoglobin for the reaction to occur. We have found that studies by ultrasonic spectroscopy can provide useful information. (2) Electron transfer process in protein molecules is probably one o f the most fundamental ones in life as it is related to the generation o f usable energy in all living matters. In the in itia l stage o f energy production, electrons are released by the breaking down o f food stuffs in animals and by the absorption o f sunlight in plants. Subsequently, these electrons are transferred through a chain o f protein carriers before being taken up by oxygen. These electron transfer reactions are exothermic and part o f the energy released is used to produce ATP molecules which are responsible for driving all chemical processes in living cells. In our laboratory, the electron transfer reaction between a protein and a donor molecule is initiated by exciting the donor w ith a powerful pulsed laser. This novel method has provided data covering a range o f redox potential not attainable by usual means. The results are useful for a better understanding o f the transfer mechanism. A t present, the work is also being extended to nonbiological molecules w ith the hope that, in the future, our study w ill help to find other efficient means o f harvesting solar energy by mimicking the photosynthetic process in nature. Biophysics o f Muscle -A .F . Leung The research attempts to provide answers to a fundamental question about the muscular system. The question is: what are the molecules doing when the muscle is working. The answers would help scientists to design drugs to eliminate any malfunction o f the system. The research is carried out by using a laser beam to illuminate the muscle. The beam is subse­ quently scattered by the molecules inside the muscle. Analyses on the patterns o f scattered light have provided for the first time several important features about molecular motions in working muscle. In addition, they also produce some insight into the way by which muscular contraction is regulated. A set o f equations linking the observed pattern o f scattered light to the internal structure o f the muscle has been developed. Recently, these equations have been used to correlate the subunits o f cardiac muscle w ith the corresponding light pattern. This cardiac muscle research ， conducted in collaboration w ith Dr. Kenneth Roos o f the Cardiovascular Research Laboratory at the Medical School o f the University o f California at Los Angeles, has received worldwide attention. Besides, my collaboration w ith Professor Joseph C. Hwang and Ms. Y.M. Cheung o f the Depart­ ment o f Physiology, University o f Hong Kong, focuses on the use o f laser light scattering method to monitor the effects o f chemical agents on muscle fibres. We have now a clear understanding o f what molecules are doing during muscular activity. How­ ever, it is still unclear as to how these molecules can generate mechanical energy necessary for motion. Further experiments are being designed to answer this puzzling question. Polymer Physics —C.L. Choy Polymers are made up o f long-chain molecules. This class o f materials is now widely used not only in everyday life but also in advanced technology including the aerospace industry. The usefulness o f a polymer in any specific application is determined largely by its properties. Therefore, to further extend the range o f applications it is necessary to have a thorough knowledge o f the physical properties and their relationship to the structure o f the materials. Polymer research was initiated in the Physics RECENT DEVELOPMENTS 25