Synthesis of phytanic acid

Preparation of methyl phytanate from phytol by catalytic hydrogenation and chromic oxide oxidation is described. The method was applied to the preparation of methyl phytanate-(14)C.     

The ablastin phenomenon: inhibition of membrane function.

Autoradiography of Trypanosoma lewisi labeled in vivo with ³H-thymidine (³HTdR) shows that the shortest doubling time for labeled organisms is 8 hr in intact and immunosuppressed rats. The parasite doubling time increases progressively after the fourth day of infection to 12 hr in immunosuppressed rats and to 24 hr or more in intact rats. The number of days following infection during which the trypanosomes reproduce is prolonged in immunosuppressed rats. In vitro studies of ablastin using ³HTdR-labeled trypanosomes confirmed that cell reproduction halts in the presence of ablastin, but resumes when the parasites are removed from the antibody. Several lines of evidence have been obtained, indicating that the primary effects of ablastin may be on membrane function. Thus, the saturable component for glucose transport in reproducing and ablastin inhibited trypanosomes has an average K_m value of 2.8 × 10^?4M, but the average V_max values for glucose transport are reduced from 3.15 nmole/min/1.25 × 10⁷ reproducing parasites to an average of 1.8 nmole/min/1.25 × 10⁷ nonreproducing forms. Glucose transport is competitively inhibited by 2-deoxyd-glucose (2DOG). The exit and counterflow of ¹⁶C-2DOG from previously loaded trypanosomes is restricted in the presence of antiserum.     

The effects of the methylating agent 1,2-bis(methylsulfonyl)-1-methylhydrazine on morphology, DNA content and mitochondrial function of Trypanosoma brucei subspecies

Repeated exposure of trypanosomes in vitro or in vivo to low concentrations of the methylating agent 1,2-bis(methylsulfonyl)-1-methylhydrazine induces a series of moderately synchronous morphological and biochemical changes. Cell division halts and the long-slender bloodstream forms transform to short-stumpy forms via larger intermediate-stage cells which contain approximately double the normal G2 content of DNA. In common with naturally occurring short-stumpy trypanosomes, drug-induced short-stumpy forms do not infect rodents and when transferred to Cunningham's medium, transform to and replicate as procyclics. Furthermore, these short-stumpy forms exhibit alpha-ketoglutarate supported motility and oxygen consumption, acquire the ability to reduce nitroblue tetrazolium (NADH diaphorase positivity) and appear to be in the G1 or G0 stage of the cell cycle based upon DNA content.     

Conformational states of poly(L-tyrosine) in aqueous solution.

Poly(L -tyrosine) [(L -Tyr)_n] has been characterized in aqueous solution using circular dichroism (CD) and infrared (ir) spectroscopy, and ultracentrifugal analysis. Most of the experiments were carried out at 0.01% polymer or less to avoid the complications caused by precipitation previously encountered by others. This permitted us to study solutions of (L -Tyr)_n at lower pH values than had been attained previously. Our results show that a transition to an antiparallel-β conformation occurs at pH 11.32 upon titration from higher pH. The β structure is intramolecular when first formed and aggregates with time or upon titration below pH 11. Ultracentrifugal analysis of the intramolecular β conformation shows that it is quite compact, with a frictional coefficient ratio, f/f_min, of 1.09. In addition to the β structure, a nonordered form of the polymer has been obtained below pH 11 by rapid titration of the ionized polyelectrolyte. This form is nonaggregated and was found to have an f/f_min of 1.01, and is therefore almost spherical. The aggregated β form was found to be thermodynamically more stable than the nonordered form at pH 10.7.