Structural modification of S-trityl-L-cysteine. Preparation of some S-(substituted trityl)-L-cysteines and dipeptides of S-trityl-L-cysteine

Abstract

A continued study of structural modification of S-trityl-L-cysteine reveals that for antileukemic activity, steric requirements of the trityl position appear to be more important than consideration of electron localization, hydrocarbon activity, or free radical stability. Activity of certain S-trityl-L-cysteinyl amino acids is observed but is of lesser degree than that of the parent S-trityl-L-cysteine. N-Substituted dipeptides and derivatives of S-trityl-L-cysteine are devoid of activity. Monohydroxymethyl-substituted S-trityl-L-cysteine still retains the original activity whereas the corresponding bis(hydroxymethyl) analog is inactive.

Experimental Study on Bubble Rising and Descending Velocity Distribution in a Slurry Bubble Column Reactor

“…The technique of using a conductivity probe to determine the bubble size and bubble velocity in gas-liquid flows was proposed by Neal and Bankoff [8]. The measurement principle and different signal analysis methods for the case of a dual-tip probe can be found in previous literature [9][10][11]. It is based on changes in the conductivity of the medium at the sensitive tip.…”

“…The signals were sampled and recorded by the computer. Bubble velocity was obtained from the distance between the two tips (l) and the interval of bubble flight from the first probe sensitive tip to the second (dt) [9,12]. So when P a was arranged below P b , the parameters of rising bubbles could be measured and when P b was arranged below P a , the parameters measured were of descending bubbles.…”

Is there any evidence for extra-dimensions or quantum gravity effects from the delayed MeV–GeV photons in GRB 940217?

“…An other possible source for the 18 GeV photon in the GRB 940217 observation is the collision between the high energy (in the TeV range) gamma-ray photons, produced in a GRB emission, and the diffuse background of microwave or infra-red photons, leading to electron-positron pair production. The pairs produced will scatter off the background photons, and since the number density of microwave background photons is significantly higher than that of infra-red photons, many 2.7 K microwave radiation photons will be boosted to a very high energy, in the (MeV-GeV) range [5], [6]. The spectrum of the scattered cosmic microwave photons has a power law form [5], [7].…”

“…Photon-pair electromagnetic cascades can produce delayed MeV-GeV photons [6]. In [15] autocorrelation was used to determine the duration of substructures in different energy bands of selected bursts.…”

Solid Phase Extraction and Spectrophotometric Determination of Silver with 2-(2-Quinolylazo)-5-diethylaminophenol as Chromogenic Reagent

“…For this reason, a wide variety of spectrophotometric methods for the determination of silver have been reported. [2][3][4][5][6][7][8][9][10][11][12][13][14] Each chromogenic system has its advantages and disadvantages with respect to sensitivity, selectivity and rapidity. Some 2-quinolylazo reagents had been reported for the determination of metal ions.…”