The time resolved emission spectra of peptide conformers measured by pulsed laser excitation

The fluorescence decays of a number of peptides were measured using pulsed laser excitation and time correlated single photon counting techniques. In all cases double exponential kinetics were observed with the short lifetime component (0.5 – 0.85 ns) predominating over the long lifetime componet (1.62 – 2.21 ns). The lifetimes varied with the peptides measured. The time resolved emission spectra of LysTrpLys shows both components have similar spectral maxima at 345 nm. It is suggested that the dual exponential kinetics originate from different conformers of the peptides.     

Anisakis simplex and Anisakis physeteris: physicochemical properties of larval and adult hemoglobins

To resolve the taxonomic relationship between two types of parasitic nematode larvae (Type I and II) and two species of parasitic nematode adults (Anisakis simplex and A. physeteris) of the aquatic ascarid genus Anisakis, collected in Japanese coastal water, a comparison was made of their hemoglobins' physicochemical properties. The larval hemoglobins were more similar to each other in electrophoretic pattern than to either adult, indeed there were few similarities whatsoever in these patterns of larval and adult hemoglobins. However, isoelectric points were 6.2 for the Type I larva and for A. simplex and 5.4 for the Type II larva and for A. physeteris. All samples showed identical patterns in spectrophotometric scanning. The circular dichroic spectra of the samples were also virtually identical, although slight differences were noted in the oxygenated hemoglobins; the Type II larva and A. physeteris exhibited a small positive peak at 575 nm but the Type I larva and A. simplex exhibited a much smaller peak (negative position). The sedimentation coefficients of the samples possessed essentially identical values (11.2–12.4). The molecular weights of the samples were estimated, roughly, to be in the range 33 to 43 × 10⁴ by thin-layer chromatography on Sephadex G-200. The evidence suggests that a relationship may exist between the Type I larva and A. simplex, and between the Type II larva and A. physeteris.     

Early hominid body weight and encephalization

The body weight of the Plio-Pleistocene hominids of Africa is estimated by predicting equations derived from the Terry Collection of human skeletons with known body weights. About 50% of the variance in body weight can be accounted for by vertebral and femoral size. Predicted early hominid weights range from 27.6 kg (61 lb) to 54.3 kg (119 lb). The average weight for Australopithecus is 43.2 kg (95 lb) and for Homo sp. indet. from East Rudolf, Kenya, is 52.8 kg (116 lb). These estimates are consistent even if pongid proportions are assumed. Indices of encephalization show that the brain to body weight ratio in Australopithecus is above the great ape averages but well below Homo sapiens. The Homo sp. indet. represented by the KNM-ER 1470, O.H. 7 and O.H. 13 crania have encephalization indices above Australopithecus despite the greater body weight of the former.     

Molecular weight and amino acid composition of purified spinach beet phenolase

The purification of spinach beet phenolase has been modified to include equilibration of the crude macerate with 0.5% cetyl-trimethylammonium bromide a     

Serum Proteins Promoting [3H]Thymidine Uptake by Trypanosoma (Schizotrypanum) cruzi (Chagas) in vitro

SYNOPSIS. Five proteins capable of stimulating [³H]thymidine uptake by Trypanosoma cruzi in vitro were isolated from fetal calf serum by (NH₄)₂SO₄ precipitation and ion exchange column chromatography. The proteins were partially characterized by immunodiffusion, immunoelectrophoresis, polyacrylamide gel disc electrophoresis, and SDS electrophoresis. As estimated by SDS electrophoresis, using 4 standards, the molecular weight of protein 1 was 100,000, that of protein 2 was 76,000. and that of proteins 3–5 was 68,000 daltons.     

Critical threshold meal size and molt initiation in Rhodnius prolixus

The molting process and body growth in Rhodnius prolixus (Hemiptera: Reduviidae) (Ståhl, 1859) are significantly influenced by the availability and quality of food. Based on the body weight of each stage, the present study provides estimates of a potential critical weight threshold required for molt initiation in R. prolixus. In addition, a new measure given by the area under the weight curve is proposed, which encapsulates both body weight and time. It is shown that this measure is consistent with the data, and allows the estimation of a pre‐refractory period (i.e. the time interval between the moment at which the critical weight threshold is reached and the moment when no further meals are accepted). The present analysis estimates the critical weight threshold as 1.6, 5.3, 12.9, 42.0 and 97.0 mg for stages 1–5, respectively, whereas the values of the area under the curve threshold as 5, 16, 31.2, 159.7 and 329.9 mg days for stages 1–5, respectively. The results of the present study confirm the existence of a weight‐dependent mechanism for the initiation of molting in R. prolixus.