On the reaction of 2-aminopropionitrile in aqueous media

The reactions of 2- and 3-aminopropionitrile (APN), and 2,2-iminodipropionitrile (IDPN) were carried out in aqueous ammoniacal media. 2-APN was found to give IDPN, N-(1-cyanoethyl)alanine amide, N-(1-cyanoethyl)alanine, N-(1-carbamoylethyl)alanine, 2,2-iminodipropionic acid, alanine amide, and alanine. Compounds of biological significance such as peptides and amino acids other than alanine were not formed. The results were well consistent with those obtained for aminoacetonitrile. IDPN which can be formed easily from 2-APN in aqueous media, also yielded the same products as with 2-APN. On the other hand, 3-APN gave 3-alanine via 3-alanine amide under similar conditions. 3-APN was found to be more stable than 2-APN in aqueous media.     

Plant leaf and stem proteins. I. Extraction and electrophoretic separation of the basic, water-soluble fraction

Simplified but highly reproducible extraction and electrophoretic procedures have been developed for plant stem and leaf proteins using recent chemical and technical advances. The method is applied to the separation of the basic, water-soluble proteins found in stem and leaf tissues of 3 Dianthus clones. While most of the highly reproducible protein bands appear in all 3 selections, and many are also common to both leaf and stem tissue, others are characteristic for the variety or tissue.     

Toxoplasmosis and the epidemiological status of the population. I. The general characteristics of the basic epidemetrons

The general characteristic of the main indices, or epidemic values (epidemetrons) is presented and the possibility of their use for characterizing the epidemiological state of the population in the foci of toxoplasmosis is evaluated.     

Genetical ESS-models. I. Concepts and basic model

Evolutionarily Stable Strategies (ESS) in phenotypic models are used to explain the evolution of animal interactive behaviour. As the behavioural features under consideration are assumed to be genetically determined, the question arises how underlying a genetical system might affect the results of phenotypic ESS-models. This question can be fully treated in terms of ESS-theory. A method of designing Genetical ESS-Models is proposed, which transfers the question of evolutionary stability to a "lower" level, the genetical basis. Genetical ESS-models - although nonlinear even in the simplest cases - can be analysed in a way that is familiar to ESS-theorists and yield immediate results on gene pool ESSs, which then may or may not maintain ESSs on the phenotypic level. Moreover, general results can be obtained to characterize evolutionarily stable gene pool states and their interrelation with commonsense, phenotypic ESSs. This part of the article presents the basic concepts and an outline of the method of genetical ESS-models. It gives, as a demonstration, a complete analysis for phenotypic two-strategy models (linear or nonlinear) based on a diploid, diallelic single-locus system under random mating. The results in this case suggest that a phenotypic ESS should indeed be expected to evolve but, maybe, only after passing through a succession of temporarily stable states.     

The behaviour of transporting epithelial cells. I. Computer analysis of a basic model.

We analyse the non-steady state behaviour of a computer model representing functional epithelial cells. The results show that a simple model of an epithelium, containing the essential ion transport asymmetries of the original Koefoed-Johnsen-Ussing model, predicts much of the observed behaviour of 'tight-type' epithelia under various well characterized experimental conditions.     

The host cell fraction that increases the infectivity of bacteriophage f2.

A fraction that increases infectivity of bacteriophage f2 was isolated from uninfected E. coli cells. The greatest effect was obtained when the fraction was added to the phage reconstituted in vitro. The fraction isolated from the ribosome-free supernatant consisted of proteins, lipids, carbohydrates, and unidentified material. Cleavage of protein by the treatment with trypsin did not significantly affect the infectivity-restoring activity. It is suggest that lipids may play an essential role in the activity of the fraction isolated from the host cell.     

Polymerization of amino acid derivatives by polymer catalysts. I. Polymerization by poly-2-vinylpyridine

Polymerizations of D ,L -β-phenylalanine, p-nitro-D ,L -β- phenylalanine, and o,p-dinitro-D ,L -β-phenylalanine NCA's were carried out with the use of α-picoline or poly-2-vinyl-pyridine as initiator. Polymerizations induced by the polymer catalyst were always faster than those with α-picoline in the same base concentrations. Furthermore, the polymer effect was more marked when the number of nitro groups in the NCA's increased. It was considered that the polymer catalyst interacts with the NCA's primarily by hydrogen bonding and increases the effective concentration of NCA along the chain. The increase of the NCA concentration in the vicinity of the polymer catalyst wits also achieved through charge-transfer complexes between nitrophenyl groups in the NCA's and pyridine groups in the polymer catalyst. As the polymer chain is flexible, a collision between an adsorbed NCA and a pyridine unit in the same polymer chain is favored, thus increasing the polymerization rate.     

The basic reproduction ratio for sexually transmitted diseases: I. Theoretical considerations.

It is shown how one can calculate the basic reproduction ratio R0 for infectious disease models where an arbitrary but finite number of disease states are recognized and where the phenomena of pair formation and separation are taken into account. Several examples are discussed.