Molecular engineering of the hole-transporting material spiro-OMeTAD via manipulation of alkyl groups

Aliphatic substituent effects on the HOMO energy levels and the ability to transport charge and form stable molecular glasses of systematically modified spiro-OMeTAD analogues were investigated.

Kinetics of 13 New Cholinesterase Inhibitors

Kinetics of hydrolysis of acetylcholine and acetylthiocholine by two types of acetylcholinesterase and butyrylcholinesterase inhibited by 13 new inhibitors (5 carbamates and 8 carbazates - hydrazinium derivatives) was measured in vitro in a batch reactor at 25 °C, pH 8, ionic strength 0.11 ᴍ and enzyme activity 3.5 U by four nondependent analytical methods. Sevin®, rivastigmin (Exelon®) and galantamin (Reminyl®) served as comparative inhibiting standards. Kinetics of hydrolyses inhibited by all studied carbamates, sevin, carbazates (with exceptions) and rivastigmin (with exceptions) can be simulated by the competitive inhibition model with irreversible reaction between enzyme and inhibitor. Galantamin does not fulfil this model. In positive simulations, the value of inhibition (carbamoylation) rate constant k3 was calculated, describing the reaction velocity between the given enzyme and inhibitor. Physiologically important hydrolyses of acetylcholine catalyzed by acetylcholinesterase from electric eel or bovine erythrocytes and butyrylcholinesterase from horse plasma can be most quickly inhibited by carbamoylation of the mentioned enzymes by the 3-N,N-diethylaminophenyl- N′-(1-alkyl) carbamates 4 and 5. Probably this is due to a long enough hydrocarbon aliphatic substituent (hexyl and octyl) on the amidic nitrogen atom. The tested carbazates failed as inhibitors of cholinesterases. The regeneration ability of the inhibited enzymes was not measured.

Characteristics of physiological inducers of the ethanol utilization (alc) pathway in Aspergillus nidulans

The ethanol utilization (alc) pathway in Aspergillus nidulans is one of the strongest expressed gene systems in filamentous fungi. The pathway-specific activator AlcR requires the presence of an inducing compound to activate transcription of genes under its control. We have demonstrated recently that acetaldehyde is the sole physiological inducer of ethanol catabolism. In the present study we show that compounds with catabolism related to that of ethanol, i.e. primary alcohols, primary monoamines and l-threonine, act as inducers because their breakdown results in the production of inducing aliphatic aldehydes. Such aldehydes were shown to induce the alc genes efficiently at low external concentrations. When ethanol is mixed with representatives of another class of strong direct inducers, ketones, the physiological inducer, acetaldehyde, prevails as effector. Although direct inducers essentially carry a carbonyl function, not all aldehydes and ketones act as inducers. Structural features discriminating non-inducing from inducing compounds concern: (i) the length of the aliphatic side group(s); (ii) the presence and nature of any non-aliphatic substituent. These characteristics enable us to predict whether or not a given carbonyl compound will induce the alc genes.

E.P.R. studies of the anions of some peri-alkylnaphthalenes

The hyperfine coupling constants for the radical anions of 2,3-dihydro- phenalene (perinaphthane) and 7,8,9,l0-tetrahydrocyclohepta[de]naphthalene have been determined from analysis of the electron spin resonance spectra in solution. The results are compared with data from other mono- and di-peri- substituted naphthalenes. A simple H�ckel molecular orbital treatment is used to describe the inductive effect of the aliphatic substituent.

Structural specificity of hexose penetration of rabbit erythrocytes

The penetration of washed rabbit erythrocytes by deoxy and O-alkyl hexoses present at an initial concentration of 20 mm in a phosphate buffer saline solution was tested in vitro. Equilibration of hexoses with intracellular water was calculated from changes in hexose concentration in the medium during incubation. Analysis of cells plus medium indicated no utilization of deoxy and O-alkyl hexoses by red cells. Alterations in the structure of glucose at individual carbon atoms by the preparation of O-methyl and deoxy derivatives was found to have little effect on the permeability of the rabbit red cells to the molecule. The entrance of such compounds was found to be temperature dependent and all of the sugars tested compete with glucose for entrance. Increasing the chain length of the aliphatic substituent on carbon 3 of glucose from methyl to butyl greatly accelerates the rate of penetration. 3-Hydroxyethyl glucose showed the most rapid rate of equilibration with intracellular water of all of the glucose derivatives tested.