New observations concerning the chloroacetaldehyde reaction with some tRNA constituents. Stable intermediates, kinetics and selectivity of the reaction.

The stable intermediates formed in the reaction of cytosine, cytidine and adenosine with chloracetaldehyde were isolated. The -CH2CH/OH/- bridge between the exo and endo nitrogen atoms of the parent base was found in these compounds by means of PMR spectroscopy. Their acid-induced dehydration resulted in formation of appropriate ethenoderivatives. The rate constants of the intermediate formation and its dehydration were found to be 38x10(-4) and 47x10(-4) /min-1/ for adenosine, and 33x10(-4) and 10x10(-4) /min-1/ for cytidine. The PH range of 4.5--5.0 was found to be optimum for both adenosine and cytidine reactions. The quantitative modification of these two nucleosides in the presence of guanosine may be achieved with high selectivity only at a low pH of 3.0--4.0 N6-methyladenosine and N4-methylcytidine react quantitatively with chloroacetaldehyde and the reaction rate is higher than in the case of the parent nucleosides. The structure of the reaction products was assigned on the basis of PMR spectroscopy.     

The X-ray structure and absolute configuration of the anticancer drug (+)-4-ketocyclophosphamide

4-Ketocyclophosphamide (4-keto CP), C7H12Cl2N2O3P, monoclinic, P2(1), a = 11.909 (2), b = 10.254 (1), c = 9.873 (1) A, beta = 91.08 (1) degrees, V = 1205.45 (3) A3 Z = 4, Dc = 1.51 Mg-m-3, Cu K alpha, lambda = 1.54178 A, alpha 25 = +53.8 degrees (c = 3.0, MeOH), m.p. 107 degrees C, mu = 61.8 cm-1, F (000) = 564, R = 0.064 for 2961 observed reflexions with I greater than 1.96 sigma(I). Dextrarotatory enantiomer of 4-keto CP has S configuration at the stereogenic center. One of the two crystallographically independent molecules is disordered both in a six-membered ring and in --N(CH2CH2Cl)2 moiety. With the exception of a less populated conformer of a disordered molecule, 4-keto CP molecules adopt a conformation in which 1,3,2-oxazophosphorinane ring is in the sofa form with C(6) deviating from the plane through the remaining five ring atoms while an exocyclic N atom with its three substituents is nearly coplanar with the phosphoryl oxygen atom O(8). In a less populated conformer, the six membered ring takes the form of sofa with C(5) as a flap while an exocyclic N atom and its substituents are oriented toward the P--N(3) bond.     

Innate immunity orchestrates the mobilization and homing of hematopoietic stem/progenitor cells by engaging purinergic signaling—an update

Purinergic Signalling - Bone marrow (BM) as an active hematopoietic organ is highly sensitive to changes in body microenvironments and responds to external physical stimuli from the surrounding...     

Postsynthetic Transformations of Oligodeoxynucleotides Originated at 6-Methylthio-purine Site

Abstract

New route to oligodeoxynucleotides labeled with fluorescent luminarine was explored. Regioselective oxidation of 6-methylthio-purines to 6-methylsulphoxides reactive toward pyridine was achieved. Upon UV irradiation of 6-pyridinium-purines oligonucleotide cleavage instead of phototransformation to luminarine was observed.     

Effect of Cytochalasin B, Lantrunculin B, Colchicine, Cycloheximid, Dimethyl Sulfoxide and Ion Channel Inhibitors on Biospeckle Activity in Apple Tissue

The biospeckle phenomenon is used for non-destructive monitoring the quality of fresh fruits and vegetables, but in the case of plant tissues there is a lack of experimentally confirmed information about the biological origin of the biospeckle activity (BA). As a main sources of BA, processes associated with the movement inside the cell, such as cytoplasmic streaming, organelle movement and intra- and extracellular transport mechanisms, are considered. The aim of this study is to investigate the effect of metabolism inhibitors, connected with intracellular movement such as cytochalasin B, lantrunculin B, colchicine, cycloheximid, dimethyl sulfoxide (DMSO) and mixture of ion channel inhibitors, injected into apples, on BA. Two methods of BA analysis based on cross-correlation coefficient and Laser Speckle Contrast Analysis (LASCA) were used. DMSO, lantrunculin B and mixture of ion channel inhibitors have a significant effect on BA, and approximately 74 % of BA of apple tissue is potentially caused by biological processes. Results indicate that the functioning of actin microfilaments and ion channels significantly affect BA.     

High salt solution structure of a left-handed RNA double helix

Right-handed RNA duplexes of (CG)_n sequence undergo salt-induced helicity reversal, forming left-handed RNA double helices (Z-RNA). In contrast to the thoroughly studied Z-DNA, no Z-RNA structure of natural origin is known. Here we report the NMR structure of a half-turn, left-handed RNA helix (CGCGCG)₂ determined in 6 M NaClO₄. This is the first nucleic acid motif determined at such high salt. Sequential assignments of non-exchangeable proton resonances of the Z-form were based on the hitherto unreported NOE connectivity path [H6_(n)-H5′/H5″_(n)-H8_(n+1)-H1′_(n+1)-H6_(n+2)] found for left-handed helices. Z-RNA structure shows several conformational features significantly different from Z-DNA. Intra-strand but no inter-strand base stacking was observed for both CpG and GpC steps. Helical twist angles for CpG steps have small positive values (4–7°), whereas GpC steps have large negative values (−61°). In the full-turn model of Z-RNA (12.4 bp per turn), base pairs are much closer to the helix axis than in Z-DNA, thus both the very deep, narrow minor groove with buried cytidine 2′-OH groups, and the major groove are well defined. The 2′-OH group of cytidines plays a crucial role in the Z-RNA structure and its formation; 2′-O-methylation of cytidine, but not of guanosine residues prohibits A to Z helicity reversal.     

The 1.19 A X-ray structure of 2'-O-Me(CGCGCG)(2) duplex shows dehydrated RNA with 2-methyl-2,4-pentanediol in the minor groove

The crystal and molecular structure of 2′-O-Me(CGCGCG)₂ has been determined at 1.19 Å resolution, at 100 K, using synchrotron radiation. The structure in space group P3₂12 is a half-turn right-handed helix that includes two 2-methyl-2,4-pentanediol (MPD) molecules bound in the minor groove. The structure deviates from A-form RNA. The duplex is overwound with an average value of 9.7 bp per turn, characterised as having a C3′-endo sugar pucker, very low base pair rise and high helical twist and inclination angles. The structure includes 65 ordered water molecules. Only a single row of water molecules is observed in the minor groove due to the presence of hydrophobic 2′-O-methyl groups. As many as five magnesium ions are located in the structure. Two are in the major groove and interact with O⁶ and N⁷ of guanosine and N⁴ of cytidine residues through their hydration spheres. This work provides the first example of molecular interactions of nucleic acids with MPD, which was used as a precipitant, cryo-solvent and resolution enhancing agent. The two MPD molecules intrude into the hydration network in the minor groove, each forming hydrogen bonds between their secondary hydroxyl group and exo-amino functions of guanosine residues. Comparison of the 2′-O-Me(CGCGCG)₂ structure in the P3₂12 and P6₁22 crystals delineates stability of the water network within the minor groove to dehydration by MPD and is of interest for evaluating factors governing small molecule binding to RNA. Intrusion of MPD into the minor groove of 2′-O-Me(CGCGCG)₂ is discussed with respect to RNA dehydration, a prerequisite of Z-RNA formation.     

Impact of nutrition on oocyte quality: cumulative effects of body composition and diet leading to hyperinsulinemia in cattle

The present study sought to assess the combined effects of body composition and diet (level of feeding) on the postfertilization developmental potential of oocytes recovered from heifers using ultrasound-guided transvaginal follicular aspiration and to relate oocyte quality to the metabolic status of these animals. By collecting oocytes on repeated occasions spanning several weeks, it was possible to assess the cumulative effects of changes in nutritional status on oocyte quality over this period. Twenty-four heifers of low and moderate body condition were placed on one of two levels of feeding (equivalent to once or twice the maintenance requirements of these animals). Oocytes were recovered at two defined time points within each of three successive estrous cycles and were matured, fertilized, and cultured to the blastocyst stage in vitro. The results show that the effect of feeding level on oocyte quality is dependent on the body condition of the animal, with the high level of feeding being beneficial to oocytes from animals of low body condition but detrimental to oocytes from animals of moderately high body condition. Furthermore, the effects of high levels of feeding on oocyte quality were cumulative, with blastocyst yields for relatively fat heifers on twice the maintenance requirement deteriorating with time relative to yields for relatively thin heifers on the same level of feeding. Finally, a significant proportion of the moderately fat animals on the high level of feeding were hyperinsulinemic, and we show, to our knowledge for the first time in ruminants, that this condition is associated with impaired oocyte quality.