The purpose of this review is to examine the various effects of low- molecular-weight electrolytes on the associations and interactions of proteins and nucleic acids. Our primary interest is in general electrostatic effects, rather than chemical effects (specific interactions) of particular ions (e.g. transition metals, protons). We consider those interactions in which a variation in salt concentration has a significant effect on the macromolecular equilibrium, and analyse the effects of salt in these situations in terms of (i) direct participation of ions in the biopolymer reaction, (ii) Debye—Hückel screening by salt ions of the charge interactions on the biopolymers, and (iii) the reduction in water activity brought about at high salt concentrations.

A sinusoidal signal is generally considered the simplest auditory signal. It is, indeed, a simple signal. However, it does not follow that a complex analysing device, like the cochlea, should treat a simple signal in a simple way. Indeed, a simple signal may appear to be complex when viewed from the standpoint of the device considered. Such an observation becomes cogent when one is attempting to discover the analysing capabilities of a device such as the cochlea, which appears designed to handle signals more complex than a sinusoid or multiple sinusoids.

The primary energy sources for all the organisms living on the Earth are either sunlight or the energy liberated during chemical transformations (mainly, oxidation) of certain substances – food. Within the cell this energy is transformed, accumulated, and then utilized to ensure a multitude of processes (synthesis of new low- and high-molecular compounds, muscle contraction, luminescence, transfer of ions counter to their concentration gradients, etc.).

The role of universal ‘energy keeper’, of the, as it were, ‘energy small change’ in biology is played by the molecules of adenosine tri- phosphate (ATP) whose hydrolytic dissociation in water solutions with the formation of adenosine diphosphate (ADP) and inorganic phosphate (P1) is accompanied by a rather strong decrease of system energy.†

The biological sciences are and should be responsive to the needs of medicine: thus the deficiency diseases (e.g. ben-ben and scurvy) stimulated the search for vitamins, just as contagious diseases fathered immunology and the study of antibiotics. It has been said that we live in the era of environmental disease, which suggests that an important fraction of human disease in technological societies is induced by environmental conditions, including some which are more commonly referred to as life styles. While this assessment requires further amplification (see below), it is clear that the sheer number and variety of potentially dangerous environmental agents has become so great that a better understanding of their fundamental interactions with the living system is clearly needed. As of the end of 1977, the American Chemical Society's Chemical Abstract Service contained over four million entities, and it is estimated that there are about 63000 chemicals in common usage. The toxicity of only a very small number of these has been investigated.

In principle, there exist two ways to contribute to structure determination of macromolecules by X-ray diffraction: (a) by analysing diffraction data obtained from the crystalline state, and (b) by interpretation of X-ray small-angle scattering from particles in solution.

The brilliant achievements of X-ray crystal-structure analysis of macromolecules, initiated by the works of Perutz on heamoglobin and Kendrew on myoglobin, are well known and it is evident that its detailed elution of secondary, tertiary and quaternary structure cannot be matched by any other means. However, a number of necessary prerequisites for a successful application, as, for example, the availability of well-defined crystals and heavy atom labelled derivatives thereof to surmount the problem of phase determination are not always given.

Resonance Raman (RR) spectroscopy provides detailed information on the vibrational and electronic properties of biochemical and biological chromophores. The analysis of RR spectra, using for example model compounds or a group frequency approach, enables us to form an accurate structural picture of the chromophore in its natural biological site. Moreover, the insight gained into the electronic states of a biological chromophore can be crucial to our understanding of its function. Thus the RR technique represents a powerful means of eliciting precise structural and electronic data from a coloured species and of focusing upon key aspects of its function. It has even been possible to obtain RR spectra from some natural chromophores in vivo, giving spectra detailed and informative enough to please a spectroscopist from a system complex enough to satisfy a biologist.

Lead is probably the oldest and most widely distributed environmental intoxicant, but unlike many of the synthetic agents which cause the greatest concern in industrial societies today, it occurs naturally at low levels in the environment and was present during evolutionary times. Galena (PbS), the most important lead-bearing mineral, is abundant and it is readily smelted. The metal is easily shaped and does not corrode and its compounds have found innumerable uses, particularly as pigments. This explains, in brief, why lead has had great economic importance since ancient times and why lead disease has plagued civilized societies for thousands of years and continues to be a serious concern to health authorities today. (Grandjean, 1975; Eisinger, 1977).

Although the importance of the polyelectrolyte character of DNA has been recognized for some time (Felsenfeld & Miles 1967), few of the implications have been explored, primarily because of a lag in translating the breakthroughs in polyelectrolyte theory of the last decade into a form that is well adapted to the analysis of the specialized problems of biophysical chemistry. Perhaps an analogous situation existed in the field of protein chemistry during the period after the formulation and confirmation of the Debye—Hückel theory of ionic solutions but before Scatchard's incorporation of the theory into his analysis of the binding properties of proteins. An achievement for polynucleotide solutions parallel to Scatchard's was recently presented by Record, Lohman, & de Haseth (1976) and further developed and reviewed by Record, Anderson & Lohman (1978).

Synchrotron radiation is intense electromagnetic radiation with a continuous spectral distribution emitted by high-energy electron (or positron) synchrotrons or storage rings in the visible, vacuum ultraviolet and X-ray regions. For a long time only an unwanted but inevitable by-product of ring accelerators in elementary particle research, synchrotron radiation is now becoming a most widely used tool in atomic, molecular and solid-state spectroscopy, surface physics, structural research on solids, soft X-ray microscopy, lithography. It is not yet clear how large the field of applications really is nor which line of research will prove to be the most fruitful one in the long run.

Serum lipoproteins are the macromolecular lipid–protein complexes, soluble in aqueous environment, which act as transport vehicles for polar and apolar lipids in the bloodstream. The growing multidisciplinary interest in these systems stems on the one hand from the fact that their physiological functions are intimately related to the pathways of lipid metabolism and catabolism, and on the other hand from their macromolecular nature which renders them accessible to a large variety of experimental approaches for the study of the physical and chemical principles of lipid-protein interaction.

In 1968 it was discovered that mercury could be biomethylated to give methylmercury as the major product (Wood, Kennedy & Rosen, 1968; Jensen & Jernelöv, 1969). This discovery has proved to be important in two respects: (a) it provided us with the recognition that biological systems are capable of synthesizing very toxic organometallic compounds from relatively innocuous inorganic precursors, and (b) it opened the door to the study of organometallic compounds produced by biological mechanisms in the aqueous environment.

As of November 1977, the American Chemical Society's Chemical Abstracts Service computer registry of chemicals contained 4039907 distinct entities, and has been growing at an average rate of about 6000 per week. How many of these chemicals are in everyday use? Current estimates from the Environmental Protection Agency indicate that there may be as many as 50000 commonly used chemicals, not including pesticides, pharmaceuticals, and food additives. The EPA estimates that there may be as many as 1500 different active ingredients in pesticides. The Food and Drug Administration estimates that there are about 4000 active ingredients in drugs and about 2000 other ancillary compounds used in the drug industry. The FDA also estimates that there are about 2500 additives used for nutritional value and flavouring and 3000 chemicals used to preserve processed food. Thus there seem to be about 63000 chemicals in common use.

Some species of minerals, when comminuted and aerosolized in the form of respirable-size particulate dusts, are recognized as capable of producing disease in man after their inhalation. Comprehensive listings of such agents are in the current literature (e.g. in Aponte, 1970; Langer & Mackler, 1972; Ehrenreich et al. 1973a, b) and many of these and their effects are well known and receive much attention. Asbestos fibres of all varieties, ampbibole and quartz contaminated talcum powders (see Rohl et al. 1976), fibrous amphiboles and their cleavage fragments which contaminate the ambient environment (e.g., the contamination of Lake Superior with cummingtonite-grunerite, as discussed in Bowes, Langer & Rohl, 1977), have been the subject of recent intensive investigations mostly due to their protential impact to large segments of the general population.