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A faint, but extensive component of broad-line ionized gas has been discovered in the peculiar giant elliptical galaxy NGC5128. This component has a radically different spatial distribution from the well-studied rotating photoionized gas associated with the dust lane although the velocity fields of the two components are similar. The origin of the broad-line gas is considered and its possible relation to the active nucleus and the X-ray jet discussed.

A ROLE for the renin-angiotensin system in the development or maintenance of increased blood pressure of spontaneously hypertensive (SH) rats has not been substantiated. These animals are considered the best model for human essential hypertension. Although there have been reports of unusually high concentrations of renin in the plasma of young SH rats2, their pathophysiological relevance has been questioned3 and, as we report here, high blood pressure is maintained even after nephrectomy. But angiotensin from the brain isorenin–angiotensin system (Iso–RAS) could be involved4,6. All the components of that system have been identified in brain tissue, including the enzyme iso-renin4–6, the substrate, angiotensinogen7, angiotensin I and converting enzyme6,8 which hydrolyses angiotensin I to form the biologically active octapeptide angiotensin II. Angiotensin II is also present in brain tissue6. When it is injected intraventricularly into the brain angiotensin II produces a prolonged increase in blood pressure9. Therefore, if angiotensin II concentrations are increased in the brains of SH rats they could be involved in the hypertensive state independently of angiotensin levels from renal origin in plasma. Using the competitive antagonist Sar-1-Ala-8-angiotensin II (saralasin acetate, P113, Norwich Pharmacal) in SH and nephrectomised SH rats, we have confirmed this possibility.

THE emergence of resistant species and an increased awareness of the environmental problems associated with the use of insecticides has resulted in a search for alternative methods of mosquito control1. One possibility is lecithin (phosphatidylcholine), which is lethal to the pupae of many species of mosquito and to some fourth stage larvae, when spread as a monomolecular layer at high surface pressure on the air–water interface2,3. Other analogous water-insoluble surfactants, such as cetyl, stearyl and oleyl alcohol ethers of ethylene glycol are equally effective, and successful trials using several of these monolayers have been carried out on rice fields in Kenya4. These have not, however, thrown much light on the mechanism of the anoxic process. Observations by high-speed photography suggested that it is not simply a decrease in surface tension, with consequent wetting of the respiratory trumpet of the insect, but also involves a physical barrier to surface penetration (demonstrated in a 35-mm film available from A.I.M.). We report here the importance of the rheological nature of the monolayer, and show that those exhibiting ‘liquid’ properties at high concentrations form efficient barriers while ‘solid’ monolayers do not. We suggest that liquidity at high surface pressure enables (1) rapid repair of the monolayer after penetration or other disturbance; (2) rapid monolayer transfer to the penetrating trumpet during its displacement from the surface followed by ‘wetting’ and the formation of a bilayer-stabilised water ‘plug’, and (3) complete coverage of the water catchment surface in spite of, for example, projecting vegetation.

SANGER1 has described the use of 1 : 2 : 4-fluoro-dinitrobenzene to identify the free amino-groups of several proteins, employing the separation of the N-dinitrophenyl amino-acids on columns of silica gel. We have had only limited success applying this method, owing to variations in different batches of the silica gel, and the difficulty of preparing evenly packed columns, which led to diffuse bands, difficult to separate. Sanger stated that with these derivatives on paper chromatograms2 long diffuse ‘tails' formed, making the method quite inferior to the silica method. We are able to report some success with the two-dimensional method, however, without apparently using any special technique which might account for the improvement. Consden et al.3 have also recently described the identification of α-δ-di- dinitrophenyl -ornithine running alone on a paper chromatogram, and Keston et al.4 using the p-I131-benzene-sulphonyl derivatives of amino-acids have been able to estimate them after their partial separation on a one-dimensional paper strip.

PHOSPHOLIPID bilayers are an important part of biological membranes1,2 and consequently their physicochemical properties have been the subject of intense investigation. There has been much discussion about how similar the properties of phospholipid bilayers are to those of membranes3–5. Because of the importance of ion transport across membranes (such as in action potentials), the question of the similarities of the intrinsic ion permeability and conductance has been raised. However, reliable information on these properties of the unmodified bilayer is scarce and the situation is confused. Here we present, for the first time, accurate sodium and chloride ion permeability measurements across both charged and uncharged unmodified phospholipid bilayers.

THE device described here has proved very useful for the rapid measurement of RF values on paper partition chromatograms1. In the figure, AB is an aluminium strip 20 in. × ½ in. × in., AC is a piece of white elastic 9 in. × ½ in. attached to the end A of the strip by sewing through a hole in the strip. The other end of the elastic C is attached to a small ‘bulldog' clip. A scale (divided into 100 parts) is marked on the elastic. For use, the zero of the scale is placed at the origin line or spot and the 100 mark stretched out to coincide with the position reached by the solvent front. The RF values of the spots can then be read off directly on the scale. While α-amino-acids can be recognized simply from their relative positions on a chromatogram, the device allows a quick check on isolated or unknown spots or the spread of a spot. A smaller apparatus on the same expanding-scale principle can be used for measuring the R value2 of substances on a column where the ratio, movement of band/movement of sample of liquid in unpacked part of the column above, is employed.

Thirst. By Barbara J. Rolls and Edmund T. Rolls. Pp.194. Hbk ISBN 0-521-22918-9; pbk ISBN 0-521-29718-4. (Cambridge University Press: 1982.) Hbk £15, $29.50; pbk £5.50, $10.95.

THERE are very few recorded observations on the temperature coefficient of contact angles1. These suggest that the coefficient is very small, if not zero, which is at first sight surprising. Adam2 has pointed out that, as a consequence, “it appears that temperature affects the surface tension and the adhesion to the solid to very nearly the same proportionate extent”. He has discussed this in terms of the thermal motions of the liquid, and has suggested that “the decrease in the adhesive field of force with rising temperature is much less in solids than in liquids and is due principally or wholly to translatory motion”. The implication, however, that the temperature coefficient of the free surface energy of solids is negligible because translatory motions are absent seems to require further justification.

WE have carried out some investigations into the conformations of whole histones and histone fractions under various conditions. The experiments on repression of DNA-dependent RNA synthesis with histones1,2, native nucleohistone3, and DNA combined with histone fractions4–10 have led to a renewed interest in the hypothesis of Stedman and Stedman11 that one of the functions of histones is the regulation of genetic activity. However, the results of the various experiments on the repression of DNA-dependent RNA synthesis are not in agreement with one another, and the inhibitory capacities of the various histone fractions appear to depend on the method of preparation of the recombined nucleohistone, particularly the relative proportions of histone and DNA used for recombination, and perhaps even on the preparation of the histone fractions themselves. These apparently conflicting results indicate the need to investigate the conformations of the histone fractions, prepared by different methods, under conditions used to reconstitute the nucleohistones.

ON account of its stability and well-defined crystalline character, insulin is a favourable point at the present time to attack protein structure. Its composition is probably better known than that of any other protein. The stoichiometrical molecular weight, that is, the least Weight into which all the analytical values can be fitted, is 12,000, indicating a comparatively simple character1. Recent researches2 show that the most prevalent molecule in aqueous solution has a molecular weight approximately four times as great, dissociating somewhat in acid and moderately alkaline solutions. The facts, therefore, suggest that the basic unit of insulin is a molecule of molecular Weight 12,000. X-ray analysis has indicated that three of these units form the unit cell in crystals3.

IT has been noticed repeatedly in this laboratory that many crystalline proteins such as chymotrypsin, serum albumin, etc., when hydrolysed in sealed tubes with 6 N hydrochloric acid at 120° C, gave a pleasant curry-like, spicy odour. A similar treatment of all the amino-acids found in proteins as well as β-alanine, α-amino-n-butyric acid, citrulline, ornithine and homocystine, showed that only threonine, allo-threonine and the derivative N-2.4.dinitrophenyl-threonine gave this odour. It was not detected in digests of threonine prepared at 110° C. in sodium hydroxide (0.005–5 N), 0.38N barium hydroxide, 18 per cent ammonium hydroxide, sulphuric acid (2–6 N), or nitric acid (0.25–2 N), but appeared weakly in 8 N acetic acid, 45 per cent formic acid and 45 per cent orthophosphoric acid digests.

A RECENT investigation1 has shown that the exchange reaction between alkylbenzenes and deuterium may provide a useful method of investigating changes in the catalytic activity of evaporated metal films subjected to thermal sintering. One of the most suitable alkylbenzenes for this purpose is p-xylene because it contains only two different kinds of hydrogen atoms—the six in the methyl groups and the four on the benzene ring. Nickel films laid down on a glass substrate at 0° C will catalyse the exchange of the first six hydrogen atoms (reaction I) about five times faster than the exchange of the remaining four (reaction II) at 0° C. Pre-sintering such nickel films for 30 min at 200° C before use reduces their activity for reaction I by a factor of about 600 but has an even more drastic effect of about 105 on the rate of reaction II. The earlier work did not establish whether these marked changes of catalytic activity on sintering were due solely to the influence of temperature on the films or whether contamination, and consequent poisoning of the films, had occurred by gas evolved from the reaction vessel. Because of this uncertainty, we have now carried out a series of experiments on the influence of carbon monoxide as a poison for reactions I and II.

The agar-plate or the cylinder-plate method of testing the effectiveness of antiseptics and antibiotics is now a well-known laboratory technique; and it is the basis of quantitative estimations of penicillin and of other antiseptics. There is little doubt that the degree of ‘zoning’ obtained is an excellent criterion of a good chemotherapeutic agent, and Fleming1 considers that this test should be so applied. However, recent experiences in my laboratory indicate that this test is not necessarily a good criterion for cation-active antiseptics of the class of quaternary ammonium salts, such as cetyl trimethyl ammonium bromide (‘Cetavlon’) and cetyl pyridinium ohloride (‘Ceepryn’).

Crossley, Northey and Hultquist1 consider that 2–(p–aminobenzenesulphonamido) pyridine has the constitution I below and not II or III mainly on the grounds that it is unchanged after prolonged boiling with concentrated caustic alkali solution.

IT has previously been reported that sodium fluoroacetate is a very effective systemic insecticide against Aphis fabae Scop.1,2. Unfortunately, its use cannot be recommended since it is a very dangerous poison, being both highly toxic and rapid in action.

WITH increasing use of chromatographic columns, the need has arisen for automatic fraction-cutting apparatus. Stein and Stanford Moore1 have devised such an apparatus in which the fraction is measured photo-electrically and the battery of receivers then moved on by an electric motor. Randall and Martin2 have recently described an ingenious mechanical fraction-cutter in which an intermittent siphon cuts the fractions. The weight of the fraction operates an escapement, bringing the siphon opposite the next receiver, the rack of receivers being stationary. In the apparatus described here, the receiver, which is depressed by the weight of the fraction, acts as the escapement. Randall and Martin used the torque of a twisted string to move the siphon delivery tube, and this idea has been copied here to move the whole rack of tubes.

SULPHAPYRIDINE (M and B 693) is readily hydrolysed by dilute mineral acids1. Many isomerides of sulphapyridine have been made and it has been found that the three isomeric derivatives from 3-aminopyridine (3-(o-, m- and p-aminobenzenesulphonamido)pyri-dine) are stable to hot mineral acids. All but one of the derivatives of 2- and 4-aminopyridine which were tested were found to be more or less easily broken down to the corresponding aminopyridine and an aminobenzene sulphonic acid as is shown below: Conditions, sulphonamide refluxed for 30 min. with 15 percent aqueous hydrochloric acid. 2-(o-aminobenzenesulphonamido)pyridine 35 percent unchanged 2-(p-aminobenzenesulphonamido)pyridine Complete hydrolysis. 4-(p-aminobenzenesulphonamido)pyridine Complete hydrolysis.

IT has been shown1 that, by the action of chymotrypsin, insulin is broken down into a number of peptide fragments of comparatively small molecular weight, and a more massive residue. The higher molecular weight material can be precipitated by means of trichloro-acetic acid. Attempts have been made to separate the lighter peptide mixture, and the most effective method so far found has been paper partition chromatography2.