远棒蚤属─新种记述(蚤目:臀蚤科)

本文记述了采自湖北省宜昌县远棒蚤属AviostivaliusTraub,1980一新种,即无端栓远棒蚤Aapapillusspnov,并对该属的属征进行了补充和修订。     

A linear correlation between energy of LMCT band and oxygenation reaction rate of a series of catecholatoiron(III) complexes: initial oxygen binding during intradiol catechol oxygenation

The oxygen reactivity of catecholatoiron(III) complexes has been examined using a series of catecholate ligands as the substrate. All the complexes examined here, [Fe(III)(TPA)(R-Cat)]BPh(4) (1-9) (TPA: tris(pyridin-2-ylmethyl)amine; R-Cat: substituted catecholate ligand, R=3,5-(t)Bu(2) (1), 3,6-(t)Bu2 (2), 3,5-Me2 (3), 3,6-Me2 (4), 4-(t)Bu (5), 4-Me (6), H (7), 4-Cl (8) and 3-Cl (9)), exclusively afforded the intradiol cleaving products of the catecholate ligands upon exposure to O2. It was revealed that 1-7 can be categorized into two classes based on their electrochemical properties; i.e., the complexes having the dialkyl-substituted (group A) and the mono- or non-substituted (group B) catecholate ligands. In spite of their classification, these two groups show a linear correlation between the logarithm of the reaction rate constant with O2 and the energy of the catecholate-to-iron(III) LMCT band, although 2 shows a large negative deviation from the correlation line. Based on this LMCT-energy dependent reactivity of 1 and 3-9 as well as the very low reactivity of 2, we have discussed on the mechanisms of the reaction of [Fe(III)(TPA)(R-Cat)]BPh4 with O2.     

Metabolites of cis,trans, and trans,cis isomers of linoleic acid in mice and incorporation into tissue lipids

Metabolism of octadecadienoic acid isomers in weanling mice was studied by feeding fat-free diets supplemented with 2% by weight of cis-9,trans-12-octadecadienoic acid (c,t-18:2-d0), tetradeuterated trans-9,cis-12-octadecadienoic acid (t,c-18:2-d4) or dideuterated cis-9,cis-12-octadecadienoic acid (c,c-18:2-d2). Rates for conversion of c,t-18:2-d0 and c,c-18:2-d2 to c,t-20:4-d0 and c,c-20:4-d2 were identical and both were 5-times higher than conversion of t,c-18:2-d4 to t,c-20:4-d4. Accumulation of t,c-18:2-d4 in liver lipids was 2-4-times higher than for c,t-18:2-d0 or c,c-18:2-d2. The t,c-18:2 diet significantly increased with the 20:3(n-9) and total lipid concentrations in liver but not in heart, plasma or brain. The 20:3(n-9)/20:4(n-6) ratio in the liver lipids was 2-4-times higher for t,c-18:2-d4 than c,c-18:2-d2 fed mice. The position of the trans bond had a marked influence on the distribution of the various intermediate desaturation and elongation products. Intermediate metabolite data for the liver lipids indicated t,c-18:2-d4 was preferentially converted to 5c,11c,14t-20:3 ('dead end' product) rather than to t,c-20:4. Concentration of the 18:3(n-6) metabolite of c,t-18:2-d0 was about 10-times greater than the 18:3(n-6) metabolite of c,c-18:2-d2. Conversely, the concentration of the normal 20:3(n-6) metabolite from c,c-18:2-d2 was 4-times higher than the 20:3(n-6) metabolite of c,t-18:2-d0. Compared to the c,c-18:2 diet, the t,c- and c,t-18:2 diets significantly increased the total n-3, but not the total n-6 fatty acid content of heart lipids. These results illustrate that the position of the trans double-bond influences a variety of enzyme activities and the isomers differ in their physiological effects.     

Leucine aminopeptidase-like activity in Aplysia hemolymph rapidly degrades biologically active alpha-bag cell peptide fragments

We have investigated the role that proteolytic enzymes in Aplysia hemolymph play in the inactivation of the neurotransmitter alpha-bag cell peptide (alpha-BCP(1-9), Ala-Pro-Arg-Leu-Arg-Phe-Tyr-Ser-Leu). alpha-BCP fragments containing Pro in positions 1 or 2, or Tyr in position 1, were degraded relatively slowly (half-life, t1/2 = 10-64 min), whereas fragments lacking these residues were degraded relatively rapidly (t1/2 = 0.5-2.7 min). Of 12 peptidase inhibitors tested, only bestatin, amastatin, and phenanthroline significantly inhibited alpha-BCP(3-9) degradation. alpha-BCP(3-9) yielded only four observable cleavage products (in order of decreasing abundance at early time points): alpha-BCP(4-9), alpha-BCP(5-9), alpha-BCP(6-9), and alpha-BCP(7-9). Degradation of alpha-BCP(3-9), alpha-BCP(4-9), alpha-BCP(5-9), alpha-BCP(6-9), or alpha-BCP(7-9) was strongly inhibited by bestatin, moderately inhibited by amastatin, and not inhibited by arphramenine B. The rates of degradation of eight alpha-BCP fragments and three other peptides in plasma were well correlated with their rates of degradation in mammalian leucine aminopeptidase (LAP, EC 3.4.11.1). Collectively our data support the following ideas. 1) In hemolymph one or more LAP-like enzymes rapidly and sequentially cleave alpha-BCP(3-9) or other small peptides lacking Pro at positions 1 or 2 or Tyr at position 1. 2) LAP-like peptidases in hemolymph may act in concert with previously described ganglionic peptidases to degrade neurally released alpha-BCP(1-9) and alpha-BCP(1-8) into inactive fragments.     

广州市十种森林生态系统的碳循环

为了探讨南亚热带森林生态系统碳循环的规律,在广泛收集资料和试验数据的基础上,对广州10种森林生态系统的碳循环进行研究.结果表明：10种森林生态系统的碳密度在108.35～151.85 t C·hm^-2,其中乔木层碳密度在10.85～48.86 t C·hm^-2,0～60 cm土壤层在87.74～99.01 t C·hm^-2,均低于全国平均水平;从大气流向植被层的碳流量为4.41～9.15 t C·hm^-2·a^-1,植被层流向土壤层的碳流量为0.74～2.06 t C·hm^-2·a^-1,土壤层流向大气层的碳流量为3.94～5.42 t C·hm^-2·a^-1,即系统从大气净吸收碳在0.47～4.97 t C·hm^-2·a^-1之间.各种林分的净系统生产力不同,阔叶林大于针叶林,混交林大于纯林,天然次生林大于人工林.     

Influence of an estrone-desulfating intestinal flora on the enterohepatic circulation of estrone-sulfate in rats

The fecal and urinary excretion of orally administered [4-14C]estrone-3-sulfate was studied in germfree (GF) rats, conventional (CV) rats and gnotobiotic rats selectively associated with estrone-desulfating and/or cecal-volume reducing microorganisms. The time required to excrete 50% of the total label recovered (t 1/2) was 22 h in CV rats vs 32 h in GF rats. Gnotobiotic rats selectively associated with a cecal volume-reducing flora (CRF rats) excreted the label even faster (t 1/2 = 13 h) than CV rats. Association of GF rats as well as CRF rats with estrone-desulfating microorganisms (termed S1 + S2 + R9 rats and CRF + S1 + S2 + R9 rats, respectively) led to a slower excretion of labeled products (t 1/2 = 38 h in S1 + S2 + R9 rats and t 1/2 = 27 h in CFR + S1 + S2 + R9 rats). Intestinal microbial desulfation also increased the relative part of the urinary excretion from 4% in GF rats to 8% in S1 + S2 + R9 rats and from 3% in CRF rats to 9% in CFR + S1 + S2 + R9 rats. We conclude that intestinal microbial desulfation enhances the enterohepatic circulation of orally administered estrone-3-sulfate.     

Influence of media composition on lactic acid production rate from whey by Lactobacillus helveticus

Summary The effect of preculture and culture media formulation on Lactobacillus helveticus lactic acid production rate was investigated in batch fermentations. Maximum lactic acid productivity of 5.5 g/l.h. was obtained from hydrolyzed whey. Clarified whey ultrafiltrate gave 4.4 g/l.h. at less expense.Nomenclature % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9qq-f0-yqaqVeLsFr0-vr% 0-vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaadaqdaaqaai% aab2eacaqGxbaaaaaa!3AF8!\[\overline {{\text{MW}}} \] peptides average molar weight - N_TK, N_NH2 total and primary -amino nitrogen concentrations (g/l) - p lactic acid concentration (g/l) - % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9qq-f0-yqaqVeLsFr0-vr% 0-vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaadaqdaaqaai% aabAfacaqGqbaaaaaa!3AFA!\[\overline {{\text{VP}}} \] lactic acid mean volumetric productivity (g/l.h.) - x total cell mass concentration (g/l)     

Structures of asparagine linked oligosaccharides of immunoglobulins (IgY) isolated from egg-yolk of Japanese quail

Structures of the Asn linked oligosaccharides of quail egg-yolk immunoglobulin (IgY) were determined in this study. Asn linked oligosaccharides were cleaved from IgY by hydrazinolysis and labelled withp-aminobenzoic acid ethyl ester (ABEE) afterN-acetylation. The ABEE labelled oligosaccharides were then fractionated by a combination of Concanavalin A-agarose column chromatography and anion exchange, normal phase and reversed phase HPLC before their structures were determined by sequential exoglycosidase digestion, methylation analysis, HPLC, and 500 MHz¹H-NMR spectroscopy. Quail IgY contained only neutral oligosaccharides of the following categories: the glucosylated oligomannose type (0.6%, Glc1-3Glc1-3Man₉GlcNAc₂; 35.6%, Glc1-3Man_7–9GlcNAc₂). oligomannose type (15.0%, with the structure Man_5–9GlcNAc₂) and biantennary complex type with core structures of-Man1-3(-Man1-6)Man1-4GlcNAc1-4GlcNAc (9.9%),-Man1-3(GlcNAc1-4)(-Man1-6)Man1-4GlcNAc1-4GlcNAc (25.1%) and-Man1-3(GlcNAc1-4)(-Man1-6)Man1-4GlcNAc1-4(Fuc1-6)GlcNAc (11.4%). Although never found in mammalian proteins, glucosylated oligosaccharides (Glc₁Man_7–9GlcNAc₂) have been located previously in hen IgY.Abbreviations IgG, IgM, IgA, IgY immunoglobulin G, M, A and Y, respectively - ABEE p-aminobenzoic acid ethyl ester     

An efficient access to protected disialylated glycohexaosyl threonine present on the leukosialin of activated T-lymphocytes

The total synthesis of the threonine-linked core 2 class disialylated hexasaccharide in a completely protected form was accomplished for the first time. The L-threonine conjugate, N-(9-fluorenylmethoxycarbonyl)-O-[(5-acetamido-4,7,8,9-tetra-O-ben zyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylonic acid)-(2-->3)-(2,6-di-O-benzyl-beta-D-galactopyranosyl)-(1-->4)-2-acetam ido-2-deoxy-3,6-di-O-benzyl-beta-D-glucopyranosyl-(1-->6)-[(5-acetamido- 4,7,8,9-tetra-O-benzyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulo pyranosylonic acid)-(2-->3)-2,6-di-O-benzyl-beta-D-galactopyranosyl-(1-->3)]-2-acetami do-2-deoxy-alpha-D-galactopyranosyl-(1d-->4c:1f-->4e)-dilactone ]-L-threonine allyl ester was synthesized via stereocontrolled glycosylations employing readily accessible monosaccharidic blocks; t-butyl-diphenylsilyl-2-azido-2-deoxy-3,6-di-O-benzyl-beta-D-gluco pyranose, N-(9-fluorenylmethoxycarbonyl)-O-(2-azido-6-O-t-butyldimethylsilyl -2-deoxy-alpha-D-galactopyranosyl)-L-threonine allyl ester, 8, 9 and N-(9-fluorenylmethoxycarbonyl)-O-(2-azido-4,6-O-benzylidene-3-O-ch loroacetyl-2-deoxy-alpha-D-galactopyranosyl)-L-threonine allyl ester. For the introduction of the amino acid, the azide group was used to temporarily mask the amino group of GalNAc so as to obtain an alpha-glycosidic linkage without participation from the C-2 substituent. The threonine was attached to the sugar unit at the monosaccharide stage to avoid loss of oligosaccharide at a later stage. The Fmoc and allyl ester protected amino acid at the reducing end facilitates efficient glycopeptide synthesis on solid-phase support.     

Mutation induction by γ and X-ray irradiation in tissue cultured lotus

Mutations of tissue cultured lotus were induced by treating plantlets with either acute -rays at doses of 0, 2, 3, 4, 5 or 6 krad or X-rays at doses of 0, 1, 2, 3, 4 or 5 krad. The 2-krad dose of either - or X-ray treatments resulted in a 50% survival rate. The use of - and X-rays to induce mutation in lotus resulted in 21 altered characteristics. Mutants from 1- and 2-krad of either or X-rays had long secondary roots and numerous adventitious roots. These mutants also exhibited good shoot growth and healthy rhizome development. Most plants treated with 3–5 krad of either - or X-rays exhibited abnormal characteristics including vitrification, chlorosis, deformed petioles and in addition had inhibited growth of lateral buds, secondary roots and rhizomes. All plants treated with 6 krad of -rays died within 4 weeks. Control plants had stoma lengths of 2.56 m and cytological analysis of the root tips confirmed the diploid chromosome number of 16. Two groups of aneuploid cells were achieved using irradiation at doses of 3 and 4 krad of either - or X-ray. Chromosome numbers were 2n=18 and 20 with associated stoma lengths of 3.43 and 4.34 m, respectively. Abnormal stomata (cyclocytic and deformity) were observed in plants treated with 4 krad of -ray.     

Long term t in vitro storage of lily: effects of temperature and concentration of nutrients and sucrose

Methods for long-term preservation of lily germplasm were examined. t In vitro regenerated bulblets of 10 lily (t Lilium L.) genotypes (Asiatic hybrids, Oriental hybrids, t L. longiflorum and t L. henryi) were stored for 28 months at -2 °C and 25 °C on four different media: 1/4 or full strength Murashige and Skoog nutrients with 9% (w/v) or 6% sucrose. Sprout growth, bulb growth, and viability were determined. The combination of 1/4 strength MS nutrients and 9% sucrose gave the highest reduction in sprout and bulb growth, the highest viability and the highest percentage of regrowth after 28 months of storage. At 25 °C, all lily genotypes survived 28 months of storage under these conditions. At -2 °C, Asiatic and Oriental hybrids survived 28 months of storage, whereas genotypes of t L. longiflorum and t L. henryi survived 6 months of storage, but died during prolonged storage. This revised version was published online in June 2006 with corrections to the Cover Date.     

Antifungal activity of organobismuth compounds against the yeast Saccharomyces cerevisiae: structure-activity relationship

Antifungal activity of organobismuth(III) and (V) compounds 1-9 was examined against the yeast, Saccharomyces cerevisiae. A clear structure-activity relationship was observed in these compounds. Thus, triarylbismuth dichlorides 2 [(4-YC6H4)3BiCl2: Y=MeO, F, Cl, CF3, CN, NO2] and halobismuthanes 6 [2-(t)BuSO2C6H4(4-YC6H4)BiX: Y=MeO, Me, H, Cl; X=Cl, Br, I], 7 [Bi(X)(C6H4-2-SO2C6H4-1'-): X=Cl, Br, I], 8 [2-Me2NCH2C6H4(Ph)BiX: X=Cl, Br] and 9 [4-MeC6H4(8-Me2NC10H6-1-)BiCl] showed the growth inhibition effect, while triarylbismuth difluorides 3 [(4-YC6H4)3BiF2] and triarylbismuthanes 1 [(4-YC6H4)3Bi], 4 [2-(t)BuSO2C6H4(4-YC6H4)2Bi] and 5 [4-YC6H4Bi(C6H4-2-SO2C6H4-1'-)] were not active at all irrespective of the nature of the substituents. Generation of the inhibition effect is governed by the facility of nucleophilic reaction at the bismuth center and the Lewis acidic bismuth center is an active site. Of all the bismuth compounds attempted, halobismuthanes 7 derived from diphenyl sulfone exhibited the highest activities. An X-ray crystallographic study of 7a [Bi(Cl)(C6H4-2-SO2C6H4-1'-)] revealed that the bismuth center adopts a seven-coordinated geometry, which is unusual in organobismuth(III) compounds, through the intramolecular and intermolecular coordination between the bismuth and oxygen atoms. The marked inhibition effect of 7 may be attributed to such a highly coordinated geometry, which allows the bismuth center to bind tightly with some biomolecules playing important roles in the growth of S. cerevisiae.     

Trans fatty acids promote the growth of some Lactobacillus strains

Five Lactobacillus strains (2 L. gasseri, 2 L. plantarum and 1 L. reuteri) were cultured in modified MRS medium containing fatty acids (FAs) instead of Tween 80 for 24 h at 37 degrees C, to learn the effect of saturated and unsaturated FAs on the Lactobacillus growth. Free FAs included palmitic (16:0), palmitoleic (c9-16:1), stearic (18:0), oleic (c9-18:1), elaidic (t9-18:1), cis-vaccenic (c11-18:1), vaccenic (t11-18:1), linoleic (c9, c12-18:2), conjugated linoleic (c9, t11- and t10, c12-18:2), alpha-linolenic (c9, c12, c15-18:3), alpha-eleostearic (c9, t11, t13-18:3), eicosapentaenoic (20:5), and docosahexaenoic (22:6) acids. Among free FAs, oleic acid stimulated the growth of all Lactobacillus strains, whereas palmitoleic acid had almost no affect on the Lactobacillus growth. Saturated FAs such as stearic and palmitic acids inhibited or did not affect the Lactobacillus growth. Polyunsaturated FAs such as alpha-linolenic, eicosapentaenoic and docosahexaenoic acids strongly inhibited the Lactobacillus growth at 7.6 x 10(-4) m. Octadecenoic acids such as oleic, elaidic, cis-vaccenic and vaccenic acids remarkably promoted the growth of L. gasseri, regardless of the different double bond positions and configurations. When oleic or cis-vaccenic acid was incubated with L. gasseri, the FAs was transformed to cyclopropane FAs (methyleneoctadecanoic acids) after incorporation into the cells. On the other hand, trans FAs such as elaidic and vaccenic acids incorporated into the cells were not converted to another FAs. Conjugated linoleic and alpha-eleostearic acids having a trans double bond promoted the Lactobacillus growth. The growth of L. gasseri was also stimulated by trans-rich free FAs from hydrogenated canola and fish oils. These results showed that octadecenoic acid and trans FAs had strong promotion activities for the Lactobacillus growth due to their incorporation into membrane lipids.     

Effects of lipid-esterified conjugated linoleic acid isomers on platelet function: evidence for stimulation of platelet phospholipase activity

The effects of four conjugated linoleic acid (CLA) isomers on in vitro collagen-induced human platelet aggregation and thromboxane (TXB(2), the inactive metabolite of the proaggregatory TXA(2)) production were examined. As the free fatty acid (FFA), 9t, 11t-CLA was the most effective inhibitor of these two processes (I(50)s of 2.2 and 4 microM, respectively) and the 9c, 11c-CLA was the least effective (I(50)s of 8.3 and 37 microM) of the isomers tested. When platelets were preesterified with either 25 microM 9t, 11t-CLA or 9c, 11c-CLA, CLA incorporation in total platelet lipids increased from 0.24% to 0.31% and 0.38%, and most of this increase was found to be in the phosphatidyl choline and phosphatidyl ethanolamine subclasses. The decrease in arachidonic acid (AA) content in total fatty acids or phospholipids was an order of magnitude greater. Furthermore, no significant differences between platelets prelabeled with either 9t, 11t- or 9c, 11c-CLA in the inhibition of collagen-induced aggregation and TXB(2) formation were observed. However, platelets prelabeled with 9c, 11c-CLA stimulated basal TXB(2) production (4-fold) which was not observed with platelets pretreated with either 9t, 11t-CLA, linoleic acid or stearic acid. This enhancement was associated with a 2.4-5-fold increase in the release of endogenous AA. Our results suggest that the presence of a conjugated cis, cis double bond appears to change the lipid environment sufficiently to stimulate the basal platelet phospholipase activity, which in turn increases the formation of TXB(2).     

Abacavir prodrugs: microwave-assisted synthesis and their evaluation of anti-HIV activities

The synthesis of a new series of abacavir prodrugs involving N2-substitution with various substituted benzaldehyde and ketone derivatives is described. The in vitro anti-HIV activities indicated that compound (3-(2-(4-methylaminobenzylideneamino)-6-(cyclopropylamino)-9H-purin-9-yl)cyclopentyl)methanol (3) was found to be most potent compound with EC50 of 0.05 microM and CC50 of >100 microM with selectivity index of >2000. Compound 3 was found to be 32 times more potent than the parent drug (EC50 of 1.6 microM). At pH 7.4, 37 degrees C, the hydrolytic t1/2 ranged between 120 and 240 min.     

Cytotoxic effects of the conjugated linoleic acid isomers t10c12, c9t11-CLA and mixed form on rat hepatic stellate cells and CCl4-induced hepatic fibrosis

Rat hepatic stellate cells (HSC-T6) were incubated for 24 h with 10-180 microM of t10c12 (98%), c9t11 (96%) and a mixed form (c9,t11:t10,c12; 41%:44%) of conjugated linoleic acid (CLA). The MTS dye reduction was measured to verify cell viability in a dose-dependent manner. Among the three CLAs, c9,t11-CLA exhibited the most intense cytotoxic effect on HSCs, the survival rate of which was reduced to 60% under 80 microM of treatment, while cell survival was slightly affected by the mixed form. Three CLA-induced cell deaths were determined by measuring DNA fragmentation using 4',6-diamidino-2-phenylindole staining. The degrees of DNA fragmentation were the most severe in HSC treated with 80 microM of c9,t11-CLA. The mitogen-activated protein kinase/extracellular signal-regulated kinase-kinase and mitogen-activated or extracellular signal-regulated protein kinase (MEK) 1 and 2 were not activated in the t10,c12-CLA treatment. This suggests that the MEK-dependent apoptosis signal is crucial in HSC, which is induced by c9,t11 and mixed CLA. In order to evaluate the protective effect of CLA on carbon tetrachloride (CCl4)-induced hepatic fibrosis in vivo, animals were treated with 10% CCl4 to induce hepatic fibrosis during all experimental periods. Rats were divided into two treatment groups: (1) control diet with tap water ad libitum (n=15) and (2) 1% CLA diet with tap water ad libitum (n=15). In the CLA-supplemented rat livers, alpha-smooth muscle actin-positive cells were significantly reduced around the portal vein. In addition, collagen fibers were not detected in the CLA-treated group. These results suggest that 9c,11t-CLA influences cytotoxic effect on HSC in an MEK-dependent manner and preserving liver from fibrosis.     

A quantitative appraisal of the ambivalent metal ion binding properties of cytidine in aqueous solution and an estimation of the<Emphasis Type="Italic"> anti</Emphasis>–<Emphasis Type="Italic">syn</Emphasis> energy barrier of cytidine derivatives

The recently defined versus straight-line plots for L = pyridine-type (PyN) and ortho-aminopyridine-type (oPyN) ligands now allow the evaluation in a quantitative manner of the stability of the 1:1 complexes formed between cytidine (Cyd) and Ca²⁺, Mg²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ or Cd²⁺ (M²⁺); the corresponding stability constants, , including the acidity constant, , for the deprotonation of the (N3)H⁺ site had been determined previously under exactly the same conditions as the mentioned plots. Since the stabilities of the M(PyN)²⁺ and M(oPyN)²⁺ complexes of Ca²⁺ and Mg²⁺ are practically identical, it is concluded that complex formation occurs in an outer-sphere manner, and this is in accord with the fact that in the pK_a range 3–7 metal ion binding is independent of or . Ca(Cyd)²⁺ and Mg(Cyd)²⁺ are more stable than the corresponding (outer-sphere) M(PyN)²⁺ complexes and this means that the C2 carbonyl group of Cyd must participate, next to N3 which is most likely outer-sphere, in metal ion binding, leading thus to chelates; these have formation degrees of about 50% and 35%, respectively. Co(Cyd)²⁺ and Ni(Cyd)²⁺ show no increased stability based on the hence, the (C2)O group does not participate in metal ion binding, but the inner-sphere coordination to N3 is strongly inhibited by the (C4)NH₂ group. In the M(Cyd)²⁺ complexes of Mn²⁺, Cu²⁺, Zn²⁺ and Cd²⁺, this inhibiting effect on M²⁺ binding at N3 is partially compensated by participation of the (C2)O group in complex formation and the corresponding chelates have formation degrees between about 30% (Zn²⁺) and 83% (Cu²⁺). The different structures of the mentioned chelates are discussed in relation to available crystal structure analyses. (1) There is evidence (crystal structure studies: Cu²⁺, Zn²⁺, Cd²⁺) that four-membered rings form, i.e. there is a strong M²⁺ bond to N3 and a weak one to (C2)O. (2) By hydrogen bond formation to (C2)O of a metal ion-bound water molecule, six-membered rings, so-called semichelates, may form. (3) For Ca²⁺ and Mg²⁺, and possibly Mn²⁺, and their Cyd complexes, six-membered chelates are also likely with (C2)O being inner-sphere (crystal structure) and N3 outer-sphere. (4) Finally, for these metal ions also complexes with a sole outer-sphere interaction may occur. All these types of chelates are expected to be in equilibrium with each other in solution, but, depending on the metal ion, either the one or the other form will dominate. Clearly, the cytidine residue is an ambivalent binding site which adjusts well to the requirements of the metal ion to be bound and this observation is of relevance for single-stranded nucleic acids and their interactions with metal ions. In addition, the anti–syn energy barrier has been estimated as being in the order of 6–7.5 kJ/mol for cytidine derivatives in aqueous solution at 25 °C.Abbreviations ADP^3– adenosine 5-diphosphate - AMP^2– adenosine 5-monophosphate - ATP^4– adenosine 5-triphosphate - CDP^3– cytidine 5-diphosphate - cl closed - CMP^2– cytidine 5-monophosphate - 3-CMP^2– cytidine 3-monophosphate - CTP^4– cytidine 5-triphosphate - Cyd cytidine - DNA deoxyribonucleic acid - I ionic strength - K_a acidity constant - K_I intramolecular equilibrium constant - L general ligand - M²⁺ general divalent metal ion - NTP^4– nucleoside 5-triphosphate - op open - oPyN ortho-aminopyridine-type ligand - PyN pyridine-type ligand - t-RNA transfer ribonucleic acid - Tu tubercidin (7-deazaadenosine)In honor of Professor Liang-Nian Ji on the occasion of his 70th birthday in friendship and with best wishes.     

Synthesis of A New Intercalating Nucleic Acid 6H-INDOLO[2,3-b] Quinoxaline Oligonucleotides to Improve Thermal Stability Of Hoogsteen-Type Triplexes

A new intercalating nucleic acid monomer X was obtained in high yield starting from alkylation of 4-iodophenol with (S)-(+)-2-(2,2-dimethyl-1,3-dioxolan-4-yl)ethanol under Mitsunobu conditions followed by hydrolysis with 80% aqueous acetic acid to give a diol which was coupled under Sonogashira conditions with trimethylsilylacetylene (TMSA) to achieve the TMS protected (S)-4-(4-((trimethylsilyl)ethynyl)phenoxy)butane-1,2-diol. Tetrabutylammonium flouride was used to remove the silyl protecting group to obtain (S)-4-(4-ethynylphenoxy)butane-1,2-diol which was coupled under Sonogashira conditions with 2-(9-bromo-6H-indolo[2,3-b]quinoxalin-6-yl)-N,N-dimethylethanamine to achieve (S)-4-(4-((6-(2-(dimethylamino)ethyl)-6H-indolo[2,3-b]quinoxalin-9-yl)ethynyl)phenoxy)butane-1,2-diol. This compound was tritylated with 4,4′-dimethoxytrityl chloride followed by treatment with 2-cyanoethyltetraisopropylphosphordiamidite in the presence of N,N′-diisopropyl ammonium tetrazolide to afford the corresponding phosphoramidite. This phosphoramidite was used to insert the monomer X into an oligonucleotide which was used for thermal denaturation studies of a corresponding parallel triplex.     

Kinetics of nitroxyl radical reactions. A pulse-radiolysis conductivity study.

Absolute rate-constants for the reaction of the nitroxyl free radicals TAN and TMPN with radiation-chemically-formed radicals and ions have been determined. k(TAN + X) (in M(-1) sec(-1)=4-0 X 10(9) (for X = OH-), 2-9 X 10(10) (eaq-), 8-0 X 10(9) (H-), 7-2 X 10(8) (-CH2OH), 4-0 X 10(8) (CH3CHOH), 4-3 X 10(8) ((CH3)2COH) 2-8 X 10(8) (-CH2(CH3)2COH), 5-9 X 10(7) (glucose radical), 4-0 X 10(8) (c-C5H9-), and k(TMPN + X)=3-4 X 10(9) (OH-), 7-8 X 10(9) (eq-), 4-9 X 10(9) (H-), 4-4 X 10(8) (-CH2OH), 4-9 X 10(8) (CH3CHOH), 3-6 X 10(8) ((CH3)2COH), 1-5 X 10(8) (-CH2(CH3)2COH), 4-9 X 10(7) (glucose radical), 4-3 X 10(8) (c-C5H9-). Direct measurements by means of a pulse-radiolysis conductivity technique were based on the formation and destruction of charged species in these reactions within certain pH ranges. It is indicated that the radiosensitizing nitroxyls undergo both redox and addition reactions.