Proton Sponge Zwitterions with Positively and Negatively Charged Hydrogen Bonds: Extremely Polar Organic Compounds and Interplay of [NHN] and [NHN] Properties.

Six previously unknown zwitterions with positively and negatively charged [NHN] hydrogen bonds were synthesized by acylation of 4,5-bis(dimethylamino)-1-tosylamino-8-aminonaphthalene with subsequent alkaline treatment of the resulting 8-acylamino derivatives. Using NMR and XRD measurements in conjunction with quantum chemical DFT/PBE1PBE/6-311++G(d,p) calculations, it was shown that the negatively charged [NHN] bond in such compounds commonly differs from the [NHN] bond by significantly lower linearity, higher asymmetry, and moderate to strong paramagnetic shift of the chelated NH proton signal. Among other remarkable findings, the most important are (1) unusually high polarity (μ = 21-26 D) of the obtained zwitterions, (2) sharp difference in structures of the solid 1,8-bis(tosylated) zwitterion (BTZ) grown from MeCN or DMF, and (3) registration for one of the stereoisomers of BTZ with the record short [NHN] hydrogen bridge (N···N = 2.

Structural peculiarities of tandem repeats and their clinical significance.

While it is well established that a mere 2% of human DNA nucleotides are involved in protein coding, the remainder of the DNA plays a vital role in the preservation of normal cellular genetic function. A significant proportion of tandem repeats (TRs) are present in non-coding DNA. TRs - specific sequences of nucleotides that entail numerous repetitions of a given fragment.

Oligonucleotides-transformers for molecular biology and nanoengineering.

In the present review, numerous experimental and theoretical data describing the properties of non-canonical DNA structures (NSs) are analyzed. NSs (G-quadruplex, i-motif, hairpin, and triplex) play an important role in epigenetic processes (including the genetic variability of viruses), are prone to energetically low-cost conformational transformations and can very effectively be used in the design of nanoscale devices. Numerous experimental data have been analyzed in connection with the so-called oligonucleotides-transformers (nucleotide sequences that able to fold not only into one, but also into several NSs).

Mechanisms of nitric oxide generation in living systems.

In modern chemical and biochemical studies, special attention is paid to molecular systems capable of generating nitric oxide (NO), which is one of the most important signalling molecules in the body and can trigger a whole cascade of reactions. Despite the importance of this molecule, the mechanisms of its formation in living organisms remain a subject of debate. This review combines the most important methods of releasing NO from endogenous and exogenous sources.

Lithium-Promoted Cycloaddition of Indole-2,3-dienolates and Carbon Disulfide as a One-Pot Route to Thiopyrano[4,3-]indole-3(5)-thiones.

A new approach for the annulation of a thiopyrane ring to an indole core under mild conditions was developed. Treating 2-methyl-3-acylindoles with lithium diisopropyl amide leads to the elimination of a proton from the 2-methyl group. The lithium indole-2,3-dienolates obtained were found to react with CS to give the corresponding thiopyrano[4,3-]indole-3(5)-thiones.