Dodecylphosphocholine micelles as a membrane-like environment: new results from NMR relaxation and paramagnetic relaxation enhancement analysis.

To further examine to what extent a dodecyl-phosphocholine (DPC) micelle mimics a phosphatidylcholine bilayer environment, we performed 13C, 2H, and 31P NMR relaxation measurements. Our data show that the dynamic behavior of DPC phosphocholine groups at low temperature (12 degrees C) corresponds to that of a phosphatidylcholine interface at high temperature (51 degrees C). In the presence of helical peptides, a PMP1 fragment, or an annexin fragment, the DPC local dynamics are not affected whereas the DPC aggregation number is increased to match an appropriate area/volume ratio for accommodating the bound peptides. We also show that quantitative measurements of paramagnetic relaxation enhancements induced by small amounts of spin-labeled phospholipids on peptide proton signals provide a meaningful insight on the location of both PMP1 and annexin fragments in DPC micelles. The paramagnetic contributions to the relaxation were extracted from intra-residue cross-peaks of NOESY spectra for both peptides. The location of each peptide in the micelles was found consistent with the corresponding relaxation data. As illustrated by the study of the PMP1 fragment, paramagnetic relaxation data also allow us to supply the missing medium-range NOEs and therefore to complete a standard conformational analysis of peptides in micelles.

Food habits and preferences of Vietnamese children.

In this study, information on food preferences and intake frequencies of 70 Vietnamese children was gathered by means of a questionnaire. The purpose was to compare the dietary habits of children who had been in the U.S. for more than one year with those of children arriving within the past year (1981). The results showed that children less than six years old who came to California more than one year ago consumed green leafy vegetables less frequently (p less than 0.01) and vitamin supplements more frequently (p less than 0.01) than those who came here recently. In the older groups (greater than 6 yrs), those who have been resident in the U.S. for more than one year consumed peanut butter and sweets (ice cream, pies, milkshakes) more frequently than those who had just arrived (p less than 0.001 and p less than 0.05, respectively). Older children (age greater than 6 yrs) who had been in the U.S. longer preferred American foods more than those who had just come (p less than 0.01). The majority of all children ate fruits as snacks. The consumption of rice, eggs, cheese, milk, meats and fruit juice was not significantly different in any of the four groups. This study also revealed a great need of nutrition education for the Vietnamese refugee mothers. Recommendations for planning nutrition education for this population are provided.

[Studies of the effect of tetrazine derivatives on the phanerogame germination and plantlet growth (author's transl)]. / Contribution à l'étude de l'influence de dérivés tétraziniques sur la germination et la croissance des plantules de phanérogames.

The 3,6-diethyl-hexahydro-s-tetrazine (I), the octahydro-s-tetrazino [1,2-a]-s-tetrazine (II) and their diacetylated or tetrabenzoylated derivatives were studied. (I) and (II) exhibited, on the Phanerogame germination and plantlet growth, in Petri box, an inhibitor effect, the intensity of which is of the same order as the one of 2,4 D (2.4-dichloro-phenoxyacetic acid).