The shape of the capsid of phage G, active against B. megatherium, has been studied by electron microscopy using a variety of approaches including negative staining of whole particles, examination of stereoscopic micrographs, shadowing, observations on capsids devoid of their DNA content (‘ghosts’), short and prolonged fixation and the use of single and serial ultra-thin sections. The results were conflicting. With negative staining the appearance of the capsid was not consistent with an icosahedral shape but could be related to that of an octahedron. The shape of the capsid in ‘ghost’ preparations was definitely octahedral. However, after fixing for 1h or longer and shadowing, the capsids were clearly icosahedral in shape with their sides equal to about half the length of those of the octahedron seen by negative staining. The same results were obtained by the thin sectioning technique. From a study of the two types of geometrical figures it was found that an octahedral container can be transformed into an icosahedral one with sides of half the original length if it is folded inwards on itself at 6 consecutive points. If this type of effect occurred during the preparative procedure it would account for the two apparently conflicting appearances of the capsid. Such an effect would involve a marked change or ‘jump’ through an intermediate unstable form. While it would reconcile the different results it is emphasized that such an interpretation is essentially speculative. To illustrate the complexities of the problem, an interesting geometrical exercise is presented in the Appendix.

The problem of molecular asymmetry in living organisms is resumed as all the previously suggested solutions seem to be unsatisfactory. The proposed idea is that the resolution between opposite enantiomers occurred at the biological level and the definitive choice was a consequence of genetic exchange.

An alternative model for the structure of anomalous water is proposed, in which all hydrogen atoms are involved in hydrogen bonds. Such a model seems to agree well with the main experimental properties of that substance. In particular, IR and Raman spectra can be estimated in agreement with the measurements of Lippincott and coworkers.

BiopolymersVolume 9, Issue 1 p. 116-123 Communication to the Editor An analysis of the hyperchromic spectra of alkali-melted DNA M. Ageno, M. Ageno Physics Laboratory, Istituto Superiore de Sanità, Roma 00161, ItalySearch for more papers by this authorE. Dore, E. Dore Physics Laboratory, Istituto Superiore de Sanità, Roma 00161, ItalySearch for more papers by this authorC. Frontali, C. Frontali Physics Laboratory, Istituto Superiore de Sanità, Roma 00161, ItalySearch for more papers by this author M. Ageno, M. Ageno Physics Laboratory, Istituto Superiore de Sanità, Roma 00161, ItalySearch for more papers by this authorE. Dore, E. Dore Physics Laboratory, Istituto Superiore de Sanità, Roma 00161, ItalySearch for more papers by this authorC. Frontali, C. Frontali Physics Laboratory, Istituto Superiore de Sanità, Roma 00161, ItalySearch for more papers by this author First published: January 1970 https://doi.org/10.1002/bip.1970.360090111Citations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume9, Issue1January 1970Pages 116-123 RelatedInformation

A kinetic study of the alkaline transition of DNA, in clearly defined physico-chemical conditions, is presented, which allows us to identify, within the alkaline transition region, different pH ranges, corresponding to different ratelimiting factors. This analysis brings into consideration three distinct intervals of time which characterize the whole process, namely the time necessary for full hyperchromicity to be reached, the time required for strand separation in the case of a single DNA molecule, and the time for complete denaturation to be reached in the case of a DNA solution.THE RESULTS OBTAINED FROM ULTRACENTRIFUGAL, AND SPECTROPHOTOMETRIC MEASUREMENTS, INVOLVING RAPID MIXING EXPERIMENTS, SEEM TO INDICATE THE FOLLOWING CONCLUSIONS: whereas, in the lower pH ranges considered within the transition region, the denaturation process is limited by the first time constant, this same constant becomes extremely short at higher pH. On the other hand the fact that, in the higher pH range, the second and third time constants do not coincide (the time to unwind a single T2 DNA molecule being at least one order of magnitude shorter than the time required for bulk denaturation to be reached) suggests that in this pH range the overall denaturation rate is limited by a statistical process governing the initiation of unwinding.These observations are discussed in terms of a model in which the unwinding energy is given by the electrostatic repulsions which originate in the deprotonated DNA molecule. The model itself suggests some experiment which seem to confirm it.

Currently, no pharmacological therapies treat skeletal muscle insulin resistance in pathological conditions such as type 2 diabetes, age-associated diseases, and cancer. Therefore, there is an unmet need to identify the molecular mechanisms ...The molecular events governing skeletal muscle glucose uptake have pharmacological potential for managing insulin resistance in conditions such as obesity, diabetes, and cancer. With no current pharmacological treatments to target skeletal muscle insulin ...

The ribosome is a macromolecular machine that undergoes global conformational rearrangements during translation, that involve coupled movements of ribosomal subunits, tRNAs, and the L1 stalk. However, there is a disagreement between different ...The two main steps of translation, peptidyl transfer, and translocation are accompanied by counterclockwise and clockwise rotations of the large and small ribosomal subunits with respect to each other. Upon peptidyl transfer, the small ribosomal subunit ...

In a previous paper (Ageno, 1967), a model of the hydrogen bond was proposed that gave a unique structure for water and was used for viscosity measurements. In this paper, an attempt is made to confirm some results obtained by using this model and interpretation by performing new experiments not involving viscosity measurements but using the heat of vaporization of ice and water from which the main chain length (L) of a linear chain of water molecules can be determined independently. An equation is derived for determining L as a function of the difference between the heat of vaporization of water at a given temperature and the external work done in the transformation of the liquid into saturated steam at that temperature. The results demonstrated that a water molecule can be involved in no more than 2 independent hydrogen bonds, and a primary alcohol molecule in no more than one.

A new type of interaction between denatured DNA and RNA is described, which takes place on mixing solutions of DNA and RNA at room temperature. The formation of a hybrid molecule containing RNA fragments bound to a DNA strand is revealed by the appearance of a new band in the analytical ultracentri-fuge patterns in a CsCl density-gradient on the high-density side of the band of denatured DNA. The action of nucleases, the effect of the mean molecular weight of RNA on the characteristics of the band and the importance of the ratio RNA/DNA have been studied quantitatively by analysing the ultracentrifuge patterns into their Gaussian components. The results show that when the ratio RNA/DNA is higher than 2, the ratio between the areas of the two bands is always very near unity. The denatured DNA not involved in the formation of the complex has been isolated by chromatography on a methylated albumin column and has been shown incapable of returning to the native configuration after annealing. This kind of interaction does not show species-specifity, since it also takes place in mixtures containing DNA from Bacillus stearothermophilus and RNA from Escherichia coli. So far no such interaction has been observed for DNA from E. coli.

A simple method is described for the gain stabilization of a photomultiplier in which the stabilization system does not interfere with the fast pulse spectrum to be measured. The functioning principle consists in sending a low frequency (77 Hz) and very low intensity light pulse, which gives a modulation of the photomultiplier thermionic noise, on the photocathode together with the scintillation light. The modulation frequency is then selected on the anode by a special filter. The signal obtained in this way is used to trigger a feedback circuit, which makes the photomultiplier gain constant by suitably varying its voltage.