Dissolved free amino acids (DFAAs) are important sources of carbon and nitrogen for marine bacteria. Past studies of DFAAs have reported inconsistencies between chemical (chromatographic) and microbiological (uptake h e t i c s ) measures of concentrations. We found no systematic differences in this temperate zone study of summer coastal and winter continental shelf seawater. Concentrations of individual DFAAs were in the 1 to 15 nM range and turnover hmes averaged 1 h or less in summer and about 6 h in winter. Chemical assays by high pressure liquid chromatography (HPLC) employed collection and filtration techniques minimizing ubiquitous DFAA contamination. Kinetics assays utilized trace-metal clean techniques and extremely low additions (0.02 to 3 nM) of tritiated DFAAs. Rnetic data, corrected for respiration and based on HPLC-measured specific activities of added amino acids, indicated some evidence for multiphasic uptake kinetics, even at subnanomolar additions. The general agreement between the HPLC and microbial techniques was consistent with rapid DFAA turnover and bacterial uptake rates approaching the maximum rate of the highest affinity systems, i.e. the uptake affinity constants (K,) were smaller than the ambient concentrations.

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with the oil pump. Nine and eight-tenths grams of 2,4,6triethylacetophenone came over at 112-114°( 4-5 mm.). The distillation slowed up and was discontinued at this point. After standing overnight at room temperature, the flask contained yellow crystals. These were removed, filtered and washed with a little 85% alcohol. On recrystallization from petroleum ether, 7.75 g. of product was obtained. The yields of diketone and monoketone were 32.5 and 38.4%, respectively.The monoketone was identified by means of a mixed melting point of its benzal derivative with an authentic specimen. The diketone crystallized in golden-yellow prisms melting at 75-75.5 °.

X-ray powder patterns on anhydrous sodium palmitate show that the five phases already known to occur between crystal and isotropic melt can be grouped into two basic structures. Both structures are liquid crystalline, i.e., crystalline in the direction of the long spacing and liquid-like laterally. Between the lower temperature "waxy" structure, which includes the previously known subwaxy, waxy, and superwaxy phases, and the higher temperature "neat" structure, which includes subneat and neat, there is a pronounced break in the curve of long spacing vs. temperature; in addition, the three waxy phases exhibit two diffuse short spacing rings, whereas the neat phases exhibit only one. These pattern differences lead to the interpretation that the waxy phases contain structural restraints on molecular position and motion not present in the neat phases.