Nicotine (NIC) is an oxygenic alkaloid compound exists in two forms R and S, and consists of a pyridine ring, substituted at the 3-position with an N-methyl-pyrrolidine ring. Nicotine is extracted mostly from the Nicotiana tabacum plant, and although it was made in the roots and accumulates in smaller amounts in leaves of edible plants of the nightshade family called “Solanaceae’’ such as tomat...

Drug-resistant mutants of HIV-1 protease limit the long-term effectiveness of current anti-viral therapy. In order to study drug resistance, the wild-type HIV-1 protease and the mutants R8Q, V32I, M46I, V82A, V82I, V82F, I84V, V32I/I84V and M46I/I84V were modeled with the inhibitors saquinavir and indinavir using the program AMMP. A new screen term was introduced to reproduce more correctly the...

Protonation of a free-base meso-pyrimidinyl-substituted AB(2)-corrole (H(3)AB(2)) in ethanol solution by stepwise addition of sulfuric acid has been studied in the temperature range from 293 to 333 K. The formation rate of protonated species was found to depend profoundly on the temperature at which the titration was undertaken. Two steps in the titration curve were identified at temperatures a...

By elucidating the mechanism of the simplest electrophilic substitution reaction of ferrocene, it was found that the verification of the protonation reaction has been a difficulty. In the work reported here, ab initio chemical dynamics simulations were performed at B3LYP/DZVP level of theory to understand the atomic level mechanisms of protonation and lithiation of ferrocene. Protonation of fer...

Plastocyanin is a small blue copper protein that shuttles electrons as part of the photosynthetic redox chain. Its redox behavior is changed at low pH as a result of protonation of the solvent-exposed copper-coordinating histidine. Protonation and subsequent redox inactivation could have a role in the down regulation of photosynthesis. As opposed to plastocyanin from other sources, in fern plas...

Carbon monoxide binding by displacement of a pendant hemi-labile ligand at a di-iron site can be substantially 'switched-on' via a ligand protonation pathway which is competitive with metal-metal bond protonation.

the acid-base equilibrium of lorazepam was studied by means of potentiometry andmultiwavelengths spectrophotometry. the stoichiometric equilibrium constants were determinedat 25 °c and constant ionic strength 0.1 mol l-1 (nacl). the acidity constants pk1=1.58±0.05and pk2=11.67±0.07 were found by potentiometry, and pk1=1.54±0.02 and pk2=11.61±0.03 bymulti-wavelengths spectrophotometry. potentiom...

Uma estimativa acurada das constantes de dissociação de antibióticos tetraciclina em misturas binárias acetonitrila-água é muito importante para muitas técnicas de separação, como cromatografia líquida e eletroforese capilar que usam essas misturas de solvente. Neste estudo, os valores de pK a de cinco tetraciclinas (tetraciclina, oxitetraciclina, clorotetraciclina, doxiciclina e metaciclina) f...

Phenothiazines are known to be among the compounds that reverse or modulate the multidrug resistance (MDR) of cancer cells. There is much evidence that the interactions of these reversal agents with the lipid phase of the plasma membrane are involved in the mechanism of MDR reversal. In this study, two parameters of a set of commercial phenothiazines were estimated: the phosphatidylocholine ves...