Additional evidence for two separable responses to auxin is pre-sented. The averge of 24 control experiments indicated lag times of 12.4 and 35.4 min, and maxium rates of 0.57 and 0.54 mm-hr-', for the first and second response, respectively. The auxin analog 4-azido-2-chlorophenoxyacetic add increased the lag time of the second response (but not the first), resulting in the temporal separation of the two responses. Plots of elongation rates against time, taken from the literature, alowed the characterization of the two responses in monocotyls and dicotyls. Study of published rate-time elongation curves showed that the maimum rate of the first response is frequently greater than the maximum rate of the second response; however, the maximum rate of the second response has not yet been shown to exceed the maximum rate of the first response.The short lag time between auxin application and increased elongation rate was first described by Yamaki (27) and Kohler (9). The possible implications of this work received considerable attention when Evans and Ray (3), using a unique growth apparatus that continuously measured and recorded growth, continued the earlier work of Ray and Ruesink (22). The rapid response of stem, hypocotyl, and coleoptile cells to auxin has since been cited frequently as evidence that auxin-induced cell elongation is not mediated by gene activation (21, and references therein), as first suggested by Skoog and co-workers (23,24), and later proposed for elongating cells by Nooden and Thimann (11-13) and Key and co-workers (6-8).The cytokinin, isopentenyladenine, inhibited auxin-induced elongation in long term (6-8 hr) experiments (26, and references therein). This naturally occurring hormone, however, did not inhibit the rapid response of elongating soybean hypocotyl cells to auxin. The study of the auxin-cytokinin interaction in elongating cells has produced evidence that there are separable responses to auxin (25). This possibility has been previously con- ' This research was supported by grants from the National Science Foundation (GB-36586, BMS72-02496) (6,8,21), it was the important conclusion from this work (25) that neither is it disproven by experiments which describe the fast response to auxin.The experiments described herein further characterize the separable responses to auxin, and present additional evidence that two elongation reactions to auxin do indeed occur in soybean hypocotyl cells. MATERIALS AND METHODSSoybean seedlings (Glycine max L. Merr. var. Wayne) were germinated in the dark and the elongating segment of the hypocotyl was excised as described (26), except that all procedures were performed under green light (460-590 nm) at 30 C.Hypocotyl extension was measured continuously with a linear transducer. The apparatus was modified after that reported by Green and Cummins (4). To facilitate clamping of the segment in the growth chamber, a 2-cm section, which included the 1-cm elongating section directly below the hypocotyl hook plus a centimeter of tissue basal to it, w...

A structural analog of NAD+, NICOTINAMIDE 3,N-4ethenocytosine dinucleotide (epsilonNCD+), has been synthesized, characterized, and compared in activity with the natural coenzyme in several enzyme systems. The Vmax and apparent Km values were determined for NAD+, epsilonNCD+, and epsilonNAD+ (nicotinamide 1, N6-ethenoadenine dinucleotide) with yeast alcohol, horse liver alcohol, pig heart malate, beef liver glutamate, and rabbit muscle lactate and glyceraldehyde-3-phosphate dehydrogenases. The Vmax for epsilonNCD+ was as great or greater than that obtained for NAD+ with three of the enzymes, 60-80 per cent with two others, and 14 percent with one. EpsilonNCD+ was found to be more active than epsilonNAD+ with all six dehydrogenases. EpsilonNCD+ served as a substrate for Neurospora crassa tnadase, but could not be phosphorylated with pigeon liver NAD+ kinase. NAD+ pyrophosphorylase from pig liver was unable to catalyze the formation of epsilonNCD+ from the triphosphate derivative of epsilon-cytidine and nicotinamide mononucleotide, but was able to slowly catalyze the pyrolytic cleavage of epsilonNCD+. The coenzyme activity of epsilonNCD+ with dehydrogenases can be discussed in terms of the close spatial homology of epsilonNCD+ and NAD+, which may allow similar accommodations within the enzyme binding regions.

Two light-sensitive analogs of 2, 4-dichlorophenoxyacetic acid, namely 4-azido-2-chlorophenoxyacetic acid and 3-azido-5-chlorophenoxyacetic acid, have been synthesized for use as auxin photoaffinity labels. The preparation and biological activity of the compounds are described. Both contain the photolabile azido group; the 2,4-substituted compound shows auxin activity and the 3,5-substituted compound does not. These photoaffinity analogs of 2, 4-dichlorophenoxyacetic acid may be useful in the identification of the auxin receptor molecules in plant cells and eventually of the receptor sites within these molecules.Among plant growth regulators, the auxins are generally distinguished by their promotion of cell elongation (25,29

Ditekiren (U-71038; Boc-Pro-Phe-N-MeHis-Leu-psi[CHOHCH2]-Val-Ile-(aminomethyl)pyridine ) is a potent renin inhibitor peptide and was formulated for clinical intravenous administration in acidified dextrose. This formulation of ditekiren was evaluated in vitro with human and monkey plasma as to its potential for forming a precipitate either of drug or of plasma proteins. Analysis by centrifugation showed that no drug precipitation occurred in plasma from either species at concentrations 25 times higher than anticipated in clinical studies. Results obtained by turbidimetry indicated that formulated ditekiren did not cause aggregation of human platelets or flocculation of proteins at concentrations approaching the solubility limit of the drug in plasma. Ditekiren or vehicle also caused no detectable lysis of red cells at concentrations representing 10 times the maximum clinical level. Therefore, ditekiren solutions as formulated are judged completely compatible with blood and plasma upon clinical intravenous administration.

2-propanediol , C h l o r o a c e t a l d e h y d e , Carbon-1.4 Adenosine Phosphates, C y t i d i n e Phosphates, Y e a s t tRNAPnQ I NTROD tic T I ON The r e a c t i o n of c h l o r o a c e t a l d e h y d e w i t h adenine and c y t o s i n e der i v a t i v e s t o form e t h e n o -b r i d g e d p r o d u c t s [l, 21 h a s found p a r t i c u l a r a p p l i c a t i o n a t t h e n u c l e o t i d e l e v e l . The f l u o r e s c e n t e t h e n o -b r i d g e d a d e n i n e an'd c y t o s i n e n u c l e o t i d e s have been u t i l i z e d a s s u b s t i t u t e cof a c t o r s w i t h v a r i o u s enzymes, and t h e c h l o r o a c e t a l d e h y d e r e a c t i o n h a s besn used t o modify n u c l e i c a c i d s 131. I n t h e l a t t e r c a s e , t h e f l u o r e s c e n c e o f a l , N b -e t h e n o a d e n y l a t e u n i t i s s e v e r e l y quenched i n * To whom t o a d d r e s s r e p r i n t r e q u e s t s