Photo-cycloreversion mechanism in diarylethenes revisited: A multireference quantum-chemical study at the ODM2/MRCI level.

Photoswitchable diarylethenes (DAEs), over years of intense fundamental and applied research, have been established among the most commonly chosen molecular photoswitches, often employed as controlling units in molecular devices and smart materials. At the same time, providing reliable explanation for their photophysical behavior, especially the mechanism of the photo-cycloreversion transformation, turned out to be a highly challenging task. Herein, we investigate this mechanism in detail by means of multireference semi-empirical quantum chemistry calculations, allowing, for the first time, for a balanced treatment of the static and dynamic correlation effects, both playing a crucial role in DAE photochemistry. In the course of our study, we find the second singlet excited state of double electronic-excitation character to be the key to understanding the nature of the photo-cycloreversion transformation in DAE molecular photoswitches.

Long-term trends in HIV care entry: over 15 years of clinical experience from Poland.

INTRODUCTION: Delay in HIV diagnosis and consequently late care entry with low CD4 counts remain a major challenge for the control of the HIV/AIDS epidemic. The aim of this study was to analyse the evolution of characteristics of the HIV epidemic in Poland. METHODS: Cross-sectional data were collected for 3972 HIV-infected patients followed up in 14 of 17 Polish HIV treatment centres in the years 2000-2015. Clinical data were analysed and factors associated with late presentation (baseline CD4 count < 350 cells/µL or history of AIDS-defining illness) and advanced HIV disease (baseline CD4 count < 200 cells/µL or history of AIDS) were identified. RESULTS: The majority (57.6%) of patients entered care late, while 35.6% presented with advanced HIV disease. The odds of being linked to care late or with advanced HIV disease increased consistently across age categories, increasing from 2.55 [95% confidence interval (CI) 1.46-4.47] for late presentation and 3.13 (95% CI 1.49-6.58) for advanced disease for the 21-30-year-old category to 5.2 (95% CI 1.94-14.04) and 8.15 (95% CI 2.88-23.01), respectively, for individuals > 60 years of age. Increased risks of late entry and advanced HIV disease were also observed for injecting drug users [adjusted odds ratio (aOR) 1.74 (95% CI 1.16-2.60) and 1.55 (95% CI 1.05-2.30), respectively], with lower aOR associated with the men who have sex with men transmission route [aOR 0.3 (95% CI 0.31-0.59) and 0.39 (95% CI 0.29-0.53), respectively]. The frequencies of cases in which patients were linked to care late and with advanced HIV disease decreased over time from 67.6% (2000) to 53.5% (2015) (P < 0.0001) and from 43.5% (2000) to 28.4% (2015) (P = 0.001), respectively. CONCLUSIONS: Despite improvements over time, most patients diagnosed with HIV infection entered care late, with a third presenting with advanced HIV disease. Late care entry remains common among people who inject drugs and heterosexual groups.

Content of lead and cadmium in aboveground plant organs of grasses growing on the areas adjacent to a route of big traffic.

The effect of traffic on the content of lead and cadmium in grass morphological parts-leaves, shoots, and inflorescences-was studied. The samples were taken on a part of the European route E30 (Siedlce by road). The following plants were tested: Dactylis glomerata, Arrhenatherum elatius, and Alopecurus pratensis. During the flowering of grasses, the plant material was collected at distances of 1, 5, 10, and 15 m from the edge of the road, on the strip of road with a length of 9 km. In the collected plant parts, the content of lead and cadmium using the atomic absorption spectroscopy (AAS) method was determined. The effect of distance from the road on the content of lead and cadmium was evaluated using regression equations. Average lead content in the above parts of tested grass species was 3.56, while cadmium 0.307 mg kg(-1) dry matter (DM). Lead content in plants of Alopecurus pratensis (average 4.11 mg kg(-1) DM) was significantly higher than in other grasses. The lowest cadmium content, significantly different from the other species, was found in plants of Arrhenatherum elatius (0.251 mg kg(-1) DM). Distance of sampling sites from the roadway significantly affects the differences in the content of cadmium and lead in plants. Analyzed aboveground plant organs of studied grasses were significantly different in contents of lead and cadmium. There were species differences in the proportions of cadmium concentration in various organs of plants. The obtained results indicate the possibility of species composition selection of grassland sward in areas with a higher risk of heavy metals associated with dust sedimentation.

Interaction of thymidylate synthase with the 5'-thiophosphates, 5'-dithiophosphates, 5'-H-phosphonates and 5'-S-thiosulfates of 2'-deoxyuridine, thymidine and 5-fluoro-2'-deoxyuridine.

New analogs of dUMP, dTMP and 5-fluoro-dUMP, including the corresponding 5'-thiophosphates (dUMPS, dTMPS and FdUMPS), 5'-dithiophosphates (dUMPS2, dTMPS2 and FdUMPS2), 5'-H-phosphonates (dUMP-H, dTMP-H and FdUMP-H) and 5'-S-thiosulfates (dUSSO3, dTSSO3 and FdUSSO3), have been synthesized and their interactions studied with highly purified mammalian thymidylate synthase. dUMPS and dUMPS2 proved to be good substrates, and dTMPS and dTMPS2 classic competitive inhibitors, only slightly weaker than dTMP. Their 5-fluoro congeners behaved as potent, slow-binding inhibitors. By contrast, the corresponding 5'-H-phosphonates and 5'-S-thiosulfates displayed weak activities, only FdUMP-H and FdUSSO3 exhibiting significant interactions with the enzyme, as weak competitive slow-binding inhibitors versus dUMR The pH-dependence of enzyme time-independent inhibition by FdUMP and FdUMPS was found to correlate with the difference in pKa values of the phosphate and thiophosphate groups, the profile of FdUMPS being shifted (approximately 1 pH unit) toward lower pH values, so that binding of dUMP and its analogs is limited by the phosphate secondary hydroxyl ionization. Hence, together with the effects of 5'-H-phosphonate and 5'-S-thiosulfate substituents, the much weaker interactions of the nucleotide analogs (3-5 orders of magnitude lower than for the parent 5'-phosphates) with the enzyme is further evidence that the enzyme's active center prefers the dianionic phosphate group for optimum binding.

Nucleoside phosphate analogues of biological interest, and their synthesis via aryl nucleoside H-phosphonates as intermediates.

This review presents a brief account of the chemistry and mechanistic aspects of aryl H-phosphonates, and selected applications of this class of compounds as intermediates in the synthesis of a wide range of biologically important analogues of nucleoside phosphates, and oligonucleotides, in which the phosphate moieties are replaced by other structurally related groups. The aryl nucleoside H-phosphonates, compounds of controlled reactivity, have proven to be more versatile and superior to various mixed anhydrides as synthetic intermediates, particularly for preparation of nucleotide analogues bearing P-N or P-S bonds in various configurational arrangements at the phosphate moiety.

Aryl H-phosphonates. 12. Synthetic and (31)P NMR studies on the preparation of nucleoside H-phosphonothioate and nucleoside H-phosphonodithioate monoesters.

Transformation of nucleoside H-phosphonate monoesters into the corresponding H-phosphonothioate and H-phosphonodithioate derivatives and possible side-reactions that may accompany this process were studied using (31)P NMR spectroscopy. These provided new insight into a possible mechanism involved in this transformation and constituted the basis for development of efficient methods for the preparation of nucleoside H-phosphonothioate and nucleoside H-phosphonodithioate monoesters using readily available H-phosphonate monoesters as starting materials.

[Precocious maturation of the testis associated with excessive secretion of estradiol and testosterone by Leydig cells]. / Przedwczesne dojrzewanie jadra przy nadmiernym wydzielaniu estradiolu i testosteronu przez komórki Leydiga.

We present the quantitative description of spermatogenesis in a 4.5-year-old boy with precocious puberty, where Leydig cell hyperplasia was associated with excessive secretion of testosterone (T), but predominantly with estradiol (E). The results were compared with data obtained from an age-matched group and adult men without hormonal abnormalities. We showed, that excessive secretion of T and E with relative deficiency of FSH is sufficient to induce testicular tubule maturation and qualitatively complete spermatogenesis, although with a poorer quantitative aspect.

Site-selected introduction of modified purine and pyrimidine ribonucleosides into RNA by automated phosphoramidite chemistry.

The study of modified nucleoside contributions to RNA chemistry, structure and function has been thwarted by the lack of a site-selected method of incorporation which is both versatile and adaptable to present synthetic technologies. A reproducible and versatile site-selected incorporation of nine differently modified nucleosides into hepta- and octadecamer RNAs has been achieved with automated phosphoramidite chemistry. The 5'-O-(4,4'-dimethoxytrityl-2'-O-tert-butyldimethylsilyl-ribonucleoside- 3'-O-(2-cyanoethyl-N,N-diisopropyl)phosphoramidite syntheses of m5C, D, psi, riboT, s2U, mnm5U, m1G and m2A were designed for compatibility with the commercially available major and 2'OH methylated ribonucleoside phosphoramidites. The synthesis of the m5C phosphoramidite was uniquely designed, and the first syntheses and incorporation of the two modified purine ribonucleosides are reported in detail along with that of psi, s2U, and mnm5U. Cleavage of RNA product from the synthesis support column, deprotection of the RNA, its purification by HPLC and nucleoside composition analysis are described. Modified nucleoside-containing tRNA domains were synthesized and purified in mumol quantities required for biophysical, as well as biochemical, studies. The anticodon domain of yeast tRNA(Phe) was synthesized with modified nucleosides introduced at the native positions: Cm32, Gm34, m1G37 (precursor to Y), psi 39 and m5C40. The T loop and stem was synthesized with riboT54 and the D loop and stem with D16 and D17. The E coli tRNA(Glu2) anti-codon codon domain was synthesized with mnm5U at wobble position 34, but an attempt at incorporating s2U at the same position failed. The unprotected thio group was labile to the oxidation step of the cyclical process. Chemically synthesized anticodon and T domains have been used in assays of tRNA structure and function (Guenther et al (1994) Biochimie 76, 1143-1151).

Ribosome binding of DNA analogs of tRNA requires base modifications and supports the "extended anticodon".

The efficiency of translation depends on correct tRNA-ribosome interactions. The ability of chemically synthesized yeast tRNA(Phe) anticodon domains to effectively inhibit the binding of native yeast tRNA(Phe) to poly(U)-programmed Escherichia coli 30S ribosomal subunits was dependent on a Mg(2+)-stabilized stem and an open anticodon loop, both facilitated by base modifications. Analysis of tRNA sequences has revealed that base modifications which negate canonical hydrogen bonding are found in 95% of those tRNA anticodon loop sequences with the potential to form two Watson-Crick base pairs across the loop. Therefore, we postulated that a stable anticodon stem and an open loop are prerequisites for ribosome binding. To test this hypothesis, DNA analogs of the yeast tRNA(Phe) anticodon domain were designed to have modification-induced, Mg(2+)-stabilized stems and open loops. The unmodified DNA analog neither bound to poly(U)-programmed 30S ribosomal subunits nor inhibited the binding of native tRNA(Phe). However, specifically modified DNA analogs did bind to ribosomal subunits and effectively inhibited tRNA(Phe) from binding. Thus, modification-dependent Mg(2+)-stabilized anticodon domain structures with open loops have evolved as the preferred anticodon conformations for ribosome binding.

Aminoacyl-tRNA synthetase and U54 methyltransferase recognize conformations of the yeast tRNA(Phe) anticodon and T stem/loop domain.

The enzyme-catalyzed posttranscriptional modification of tRNA and the contributions of modified nucleosides to tRNA structure and function can be investigated with chemically synthesized domains of the tRNA molecule. Heptadecamer RNAs with and without modified nucleosides and DNAs designed as analogs to the anticodon and T stem/loop domains of yeast tRNA(Phe) were produced by automated chemical synthesis. The unmodified T stem/loop domain of yeast tRNA(Phe) was a substrate for the E coli m5U54-tRNA methyltransferase activity, RUMT. Surprisingly, the DNA analog of the T stem/loop domain composed of d(A,U,G,C) was also a substrate. In addition, the DNA analog inhibited the methylation of unfractionated, undermodified E coli tRNA lacking the U54 methylation. RNA anticodon domains and DNA analogs differentially and specifically affected aminoacylation of the wild type yeast tRNA(Phe). Three differentially modified tRNA(Phe) anticodon domains with psi 39 alone, m1G37 and m5C40, or psi 39 with m1G37 and m5C40,stimulated phenylalanyl-tRNA synthetase (FRS) activity. However, one anticodon domain, with m5C40 as the only modified nucleoside and a closed loop conformation, inhibited FRS activity. Modified and unmodified DNA analogs of the anticodon, tDNA(PheAC), inhibited FRS activity. Analysis of the enzyme activity in the presence of the DNA analog characterized the DNA/enzyme interaction as either partial or allosteric inhibition. The disparity of action between the DNA and RNA hairpins provides new insight into the potential allosteric relationship of anticodon binding and open loop conformational requirements for active site function of FRS and other aaRSs. The comparison of the stimulatory and inhibitory properties of variously modified RNA domains and DNA analogs demonstrates that conformation, in addition to primary sequence, is important for tRNA-protein interaction. The enzyme recognition of various DNA analogs as substrate and/or inhibitors of activity demonstrates that conformational determinants are not restricted to ribose and the standard A-form RNA structure.

A case of renal lymphangioma with a karyotype 45,X,-X,i dic(7q).

Cytogenetic analysis of a polycystic unilateral renal lymphangioma was performed by short-term culture and banding methods. The tumor's cells showed an isochromosome of the long arm of chromosome #7 and monosomy of X chromosome, whereas the peripheral lymphocytes stimulated with phytohemagglutinin showed a normal female karyotype, 46,XX. These karyotypic anomalies suggest that lymphangioma, although clinically benign, may have malignant potential.

Clinical, hormonal and semiological data in adult men operated in childhood for hypospadias.

Examination of 16 adult men operated in childhood for hypospadias revealed signs of moderate injury of the male genital system. It appears that accessory sexual glands were mainly responsible for the observed abnormalities. Since testicular position and size, serum testosterone and FSH levels were normal it seems that hypospadias and the accompanied disturbances are connected with reduction of responsiveness of target tissues to androgen stimuli rather, than with lesion of the testicle. The coexistence of normal serum testosterone and elevation of serum LH suggests the decrease of sensitivity of hypothalamic or pituitary receptors to negative feedback influence of androgens. The consciousness of sexual inadequacy noted in some cases was mainly of emotional character.