From the results of X-ray crystallography a wealth of information is now available concerning the detailed molecular structure of proteins, nucleic acids, and membrane components. This has made it possible to apply successfully various spectroscopie techniques for time resolved studies as well as theoretical simulations of internal molecular dynamics in the biological macromolecules and molecular aggregates. We were particularly pleased to see professor Ivar Waller among the participants of the workshop since new use of the wellknown Debye–Waller factor has greatly contributed to this development. A molecular picture is presently emerging including the dimension of time which ultimately will give us a detailed understanding of the functional interactions between biomolecules in general, and in particular enzyme catalysis, nucleic acid functions, and transport of matter and information through membranes.

Psoralen photochemistry is specific for nucleic acids and is better understood at the molecular level than are all other methods of chemical modification of nucleic acids. These compounds are used both for in vivo structure analysis and for photochemotherapy since they easily penetrate both cells and virus particles. Apparently, natural selection has selected for membrane and virus penetrability during the evolution of these natural products. Most cells are unaffected by relatively high concentrations of psoralens in the absence of ultraviolet light, and the metabolites of the psoralens have thus far not created a problem. Finally, psoralens form both monoadduct and cross-links in nucleic acid helices, the yield of each being easily controlled by the conditions used during the photochemistry.

The anatomy and physiology of cornea has been described in reviews (Maurice, 1969; Davson, 1980). We are primarily concerned with the structure of the stroma of cornea. There are two levels of organization in the stroma: the collagen fibrils and the lamellae. Each lamella contains an array of collagen fibrils which appear as long thin cylinders in electron micrographs. The lamellae are parallel to the cornea surface and are at right angles to the light direction. Adjacent lamellae are approximately at right angles to each other. There are many lamellae (about 200) in the thickness of the stroma so that the different lamellae have on the average all possible orientations.

Correlating the structure and action of biological molecules requires knowledge of the corresponding relation between structure and energy. Probably the most important factors in such a structure– energy correlation are associated with electrostatic interactions. Thus the key requirement for quantative understanding of the action of biological molecules is the ability to correlate electrostatic interactions with structural information. To appreciate this point it is useful to compare the electrostatic energy of a charged amino acid in a polar solvent to the corresponding van der Waals energy. The electrostatic free energy, ΔGel, can be approximated (as will be shown in Section II) by the Born formula (ΔGel = –(166Q2/ā) (I – I/E)). Where ΔGel is given in kcal/mol, Qis the charge of the given group, in units of electron charge, āis the effective radius of the group, and E is the dielectric constant of the solvent. With an effective radius of charged amino acids of approximately 2 Å, Born's formula gives about – 80 kcal/mol for their energy in polar solvents where E is larger than 10. This energy is two orders of magnitude larger than the van der Waals interaction of such groups and their surroundings.

Photosynthesis is the conversion of the quantum energy of light into the chemical energy of complex organic molecules and organized cellular structures in plants and in some bacteria. The processes of photosynthesis span the time domain of subpicoseconds to the millennia of slow-growing trees, its study brings together such diverse disciplines as photophysics, biochemistry, botany and ecology. In the last few decades tremendous progress has been made in understanding the multivarious chemical reactions that ultimately lead to the fixation of carbon dioxide into organic substance, yet the basic mechanism underlying the conversion of photon energy into chemical energy still remains very much an enigma. These so-called primary reactions which transduce the excitation energy of excited chlorophyll pigments into the potential energy of stabilized, separated charges on electron donor and electron acceptor molecules have been studied with a variety of physical techniques, among which fast optical spectroscopy and electron paramagnetic resonance (EPR) are prominent. This review will highlight one intriguing aspect of EPR, namely that of electron spin polarization (ESP).† It will be shown that ESP of photosynthetic primary reactants offers a unique tool to gain insight in the electrostatic and magnetic interactions that make photosynthesis work. Moreover, it will become apparent that ESP in photosynthesis has several unique traits not (yet) found in ESP of photochemical reactions in vitro. As such, it may serve as a paradigma of ESP phenomena and will present an absorbing spectacle also for EPR spectroscopists outside photosynthesis.

The present study is best understood as an extension and critique of two schools of thought. The first is that of Malloe and his students, among whom we number ourselves. It is to Maaloe that we are indebted for the idea that logarithmically growing bacteria assemble and use tibosomes in amounts that are optimally adjusted to yield the maximal growth rates supported by different media. Her, we begin our analysis by applying this optimization priciple to all the components of a logarithmically growing system. Our objective is to use the growth optimization constraint as a tool to explore the physiological limits on the accuracy of gene expression. This brings us to our second source of inspiration, which is Orgel's (1963) conception of a problem that Ninio (1982) has referred to as the ‘great error loop’.

In earlier papers (Wyman, 1975a, b, 1981) I have called attention to the existence of a group of linkage potentials derivable from one another by a corresponding group of Legendre transformations. These potentials are applicable to any system in a state of equilibrium but are especially useful in the study of the behaviour, or, as we may say, the functional chemistry, of a macromolecule in the presence of its ligands. In this paper I show how these potentials may be represented by a set of contour graphs which embody the results of observation and are transformable into one another by a group of graphical permutations equivalent to the Legendre group.

Magnetization transfer techniques are specialized NMR experiments which can measure the rate of chemical reactions while concentrations of products and reactants are maintained constant. These techniques are being used to measure the rates of enzyme catalysed reactions in a variety of living systems and in vitro. The magnetization transfer measurements in vivo of the ATP synthetase and the creatine kinase reactions have been particularly useful in describing rates of major energy transducing reactions involving ATP and phosphocreatine. As a result, a wide range of biomedicai scientists are becoming aware of the potentials of these techniques. The purpose of this review is thus threefold: first, to present a concise, conceptual review of the underlying principles for these non-specialists; secondly, to review the important biochemical applications of the method which have appeared, and thirdly, to discuss potential applications and limitations of the method.