Ar、NO和CHBr3对电子激发态CH的淬灭

The collisional quenching rate constants of CH(A, V'=0) by Ar and CHBr_3 and CH(A, B, V'=0) by NO molecule were measured by means of laser photolysis of CHBr_3 molecule at 266 nm generating CH(A, B) radicals and monitoring the time-resolved signal of ethession CH(A, B→X). The dependence of quenching rate constant of CH(A, V'=0) by CHBr_3 on rotational state of CH(A) is presented. It is found that the quenching rate decreases with increasing rotational quantum number of CH(A).     

Bioinspired Total Synthesis of Complex Nucleoside Antibiotics A201A,A201D and A201E

Herein, bioinspired total syntheses of A201A, A201D, and A201E based on a previously reported biosynthetic pathway are presented. The challenging 1,2-cis-furanoside, a core structure of the A201 family, was obtained by remote 2-quinolinecarbonyl-assisted glycosylation. We accomplished the total synthesis of A201A and A201E based on the critical 1,2-cis-furanoside moiety through late-stage glycosylation without any interference from basic dimethyl adenosine. We also confirmed the absolute configuration of A201E by total synthesis. This modular synthesis strategy enables efficient preparation of A201 family antibiotics, allowing the study of their structure–activity relationships and mode of action. This study satisfies the increasing demand for developing novel antibiotics inspired by the A201 family.     

Relationship between the broad OH stretching band of methanol and hydrogen-bonding patterns in the liquid phase

The OH stretching (nu(OH)) band of methanol observed in condensed phase has been analyzed in terms of hydrogen-bonding patterns. Quantum chemical calculations for methanol clusters have revealed that broadening of the nu(OH) envelope is reasonably reproduced by considering nearest and next-nearest neighbor interactions through hydrogen bonding. Because the hydrogen bond formed between donor (D) and acceptor (A) is cooperatively strengthened or weakened by a newly formed hydrogen bond at D or A, we have proposed the following notation for hydrogen-bonding patterns of monohydric alcohols: a(D)DAd(A)a(A), where a is the number of protons accepted by D (a(D)) or A (a(A)), and d(A) is the number of protons donated by A. The indicator of the hydrogen-bond strength, which is given by M(OH) = a(D) + d(A) - a(A), is correlated well with the nu(OH) wavenumber of the methanol molecule D participating in the a(D)DAd(A)a(A) pattern. The correlation between M(OH) and the hydrogen-bonding energy of the a(D)DAd(A)a(A) pattern has also been deduced from the calculation results for the clusters. The nu(OH) bands of methanol measured in the CCl4 solution and pure liquid have been successfully analyzed by the method proposed here.     

Bioinspired Total Synthesis of Complex Nucleoside Antibiotics A201A,A201D and A201E

Herein, bioinspired total syntheses of A201A, A201D, and A201E based on a previously reported biosynthetic pathway are presented. The challenging 1,2-cis-furanoside, a core structure of the A201 family, was obtained by remote 2-quinolinecarbonyl-assisted glycosylation. We accomplished the total synthesis of A201A and A201E based on the critical 1,2-cis-furanoside moiety through late-stage glycosylation without any interference from basic dimethyl adenosine. We also confirmed the absolute configuration of A201E by total synthesis. This modular synthesis strategy enables efficient preparation of A201 family antibiotics, allowing the study of their structure–activity relationships and mode of action. This study satisfies the increasing demand for developing novel antibiotics inspired by the A201 family.     

尼龙6/多单体接枝聚丙烯共混物的形态结构及力学性能的研究

用多组分熔融接枝的方法将甲基丙烯酸缩水甘油酯（ Ｇ Ｍ Ａ） 和苯乙烯（ Ｓｔ） 共同接枝于聚丙烯（ Ｐ Ｐ） 上,制得多单体接枝聚丙烯 Ｐ Ｐ ｇ （ Ｇ Ｍ Ａ ｃｏ Ｓｔ） ．该接枝物具有高的 Ｇ Ｍ Ａ 接枝率．本研究利用 Ｆ Ｔ Ｉ Ｒ、 Ｓ Ｅ Ｍ、 Ｔ Ｅ Ｍ、 Ｄ Ｓ Ｃ 和力学性能测试等分析方法,研究了多组分熔融接枝聚丙烯（ Ｐ Ｐ ｇ （ Ｇ Ｍ Ａ ｃｏ Ｓｔ）） 对尼龙６／ Ｐ Ｐ 共混物的形态结构, Ｔｇ 和力学性能的影响．结果表明, Ｐ Ｐ ｇ （ Ｇ Ｍ Ａ ｃｏ Ｓｔ） 中的环氧基团与尼龙６（ Ｐ Ａ６） 末端的胺基发生化学反应,原位形成的 Ｐ Ｐ Ｐ Ａ６ 共聚物能有效的改善 Ｐ Ａ６ 与 Ｐ Ｐ 的相容性,可以使 Ｐ Ｐ 均匀的分散在 Ｐ Ａ６ 基体中,相区尺寸明显减小,提高了拉伸强度．由于两相的相容性较好,从而共混物的 Ｔｇ 有明显的变化．此外,通过透射电镜观察,发现 Ｐ Ａ６／ Ｐ Ｐ ｇ （ Ｇ Ｍ Ａ ｃｏ Ｓｔ）（７０／３０） 合金中存在着特殊的微相分离结构．     

Pre-resonance Raman studies of some mesogens-TB4A, TB7A and TB10A

Pre-resonance Raman spectra of certain liquid crystalline compounds, TB4A, TB7A and TB10A, are reported. The anomaly observed in the pre-resonance Raman spectra in the three compounds was initially explained by the Albrecht-Hutley Model, but its failure leads us to explain the anomalous intensity enhancement mechanism by invoking an interference effect between a weak dipole-forbidden excited state and a nearby strong electronic level via vibrational modes. The presence of a 2¹A_g dipole-forbidden excited state in TB4A and TB10A is deduced after an elaborate discussion of their centro-symmetric structure. The structural difference of TB7A in comparison with TB4A and TB10A is also discussed by taking their X-ray data into consideration.     

One-step synthesis of amino-dextran-protected gold and silver nanoparticles and its application in biosensors

A sensitive method for the detection of the lectin protein concanavalin A (Con A) was developed using amino-dextran (AD)-protected gold (AD-Au) and silver nanoparticles (AD-Ag) as sensitive optical probes. The AD-Au and AD-Ag nanoparticles were synthesized by directly applying amino-dextran as a reductive and protective reagent. The size of the nanoparticles could be altered by changing the molar ratio of AD to the metal salt. The amino-dextran bound to Con A by forming a 4:1 Au-Con A complex at neutral pH, and the nanoparticles were induced to aggregate by Con A. The absorption intensity of the nanoparticles decreased linearly with as the Con A concentration was increased from 3.85×10^–8 to 6.15×10^–7 M. The Au-Con A complex was dissociated by the disaccharide isomaltose, which has a higher affinities for Con A than Au; this competitive strategy could also be used to detect similar types of saccharides.     

尼泊金乙酯分子印迹固相萃取小柱的研制及应用

研制了一种对尼泊金乙酯具有特异性识别性能的分子印迹固相萃取小柱。用本体聚合法制备尼泊金乙酯分子印迹聚合物,通过静态平衡吸附实验及固相萃取实验表征其固相萃取性能,并结合UV法对滴眼液中的尼泊金乙酯进行测定。结果显示,尼泊金乙酯模板聚合物的吸附能力强于空白聚合物;印迹固相萃取柱对尼泊金乙酯标准溶液(0.04mmol/L)一...     

Remarkable aspects of unsaturation in trinuclear metal carbonyl clusters: the triiron species Fe3(CO)n (n = 12, 11, 10, 9)

The trinuclear iron carbonyls Fe(3)(CO)(n) (n = 12, 11, 10, 9) have been studied by density functional theory using the B3LYP and BP86 functionals. The experimentally known C(2)(v) isomer of Fe(3)(CO)(12), namely Fe(3)(CO)(10)(mu-CO)(2), is found to be the global minimum below the unbridged D(3)(h) isomer analogous to the known structures for Ru(3)(CO)(12) and Os(3)(CO)(12). The lowest-energy isomer found for Fe(3)(CO)(11) is Fe(3)(CO)(9)(mu(3)-CO)(2) with iron-iron distances in the Fe(3) triangle, suggesting the one double bond (2.460 A by B3LYP and 2.450 A by BP86) and two single bonds (2.623 A by B3LYP and 2.604 A by BP86) required to give each Fe atom the favored 18-electron configuration. Two different higher-energy dibridged structures Fe(3)(CO)(9)(mu(2)-CO)(2) are also found for Fe(3)(CO)(11). The lowest-energy isomer found for Fe(3)(CO)(10) is Fe(3)(CO)(9)(mu(3)-CO) with equivalent iron-iron distances in the Fe(3) ring (2.47 A by B3LYP or BP86). The lowest-energy isomer found for Fe(3)(CO)(9) is Fe(3)(CO)(6)(mu-CO)(3) with distances in the Fe(3) triangle possibly suggesting one single bond (2.618 A by B3LYP and 2.601 A by BP86), one weak double bond (2.491 A by B3LYP and 2.473 A by BP86), and one weak triple bond (2.368 A by B3LYP and 2.343 A by BP86). A higher-lying isomer of Fe(3)(CO)(9), i.e., Fe(3)(CO)(8)(mu-CO), at approximately 21 kcal/mol above the global minimum, has iron-iron distances strongly suggesting two single bonds (2.6 to 2.7 A) and one quadruple bond (2.068 A by B3LYP and 2.103 A by BP86). Wiberg Bond Indices are also helpful in evaluating the iron-iron bond orders.     

Total Synthesis of Siomycin A: Completion of the Total Synthesis

The total synthesis of siomycin A ( 1 ), a representative compound of the thiostrepton family of peptide antibiotics, was achieved by incorporating the five synthetic segments A ( 2 ), B ( 3 ), C ( 4 ), D ( 5 ), and E ( 6 ). The dehydropiperidine segment A ( 2 ) was esterified with the dihydroquinoline segment C ( 4 ), and the subsequent coupling with the β‐phenylselenoalanine dipeptide segment D ( 5 ) at the segment C portion followed by lactamization between the segments A and D gave segment A‐C‐D ( 27 ). This was amidated with the pentapeptide segment B ( 3 ) at the segment A portion followed by one‐pot cyclization (between segments A and B) and elongation (with the β‐phenylselenoalanine dipeptide segment E ( 6 ) at the segment A portion), thus furnishing siomycin A ( 1 ).     

The circular bacteriocins gassericin A and circularin A

Gassericin A, a bacteriocin produced by Lactobacillus gasseri LA39, shows antibacterial activity against a number of Gram-positive food-borne pathogenic bacteria. Circularin A produced by Clostridium beijerinckii ATCC25752 is active against C. tyrobutyricum, a known cheese-spoilage bacterium. Both bacteriocins were purified to homogeneity from culture supernatants by reverse-phase chromatography and the subsequently determined amino acid sequences were used to clone the bacteriocin structural genes. Mature gassericin A and circularin A are class V circular bacteriocins comprised of 58 and 69 amino acid residues, respectively. Both bacteriocins are resistant to several peptidases and proteases, as are other cyclic bacteriocins. Heterologous expression of gassericin A in Escherichia coli was used to produce a non-cyclic mature peptide, which was shown to have a specific activity 173-fold lower than the circular molecule. The minimal region for production and secretion of active circularin A is comprised of five genes, as was deduced by heterologous gene expression in Enterococcus faecalis. Gassericin A and circularin A have limited mutual similarity in their primary sequences. Unlike most bacteriocins, including gassericin A, circularin A has a three-amino-acid-leader sequence.     

Validation study of the VitaKit A test kit for the determination of vitamin A in fluid milk (2% fat) for routine quality control. Performance Tested Method 061001

A validation study of VitaKit A for quantitation of total vitamin A in 2% fluid milk was carried out according to the guidelines provided by AOAC INTERNATIONAL. The VitaKit A was compared, in terms of repeatability and accuracy, with the U.S. Food and Drug Administration-Interstate Milk Shippers HPLC reference method for determination of total vitamin A in fluid milk with 2% fat. The data obtained by the VitaKit A method are in excellent agreement with the data obtained by the HPLC reference method. Further, a low LOD (0.33 international unit/mL) was obtained for the VitaKit A method; the presence of interferents, like cholesterol and vitamin D3, in the milk had minor influence on the quantitation of total vitamin A by the VitaKit A method. The VitaKit A test kit was found to be stable for 1 year from the date of manufacture when stored at 2-8 degrees C. The method requires 2 h processing time, compared to 1-2 days for the HPLC reference method. The results of this validation study clearly demonstrate that the VitaKit A method is reliable, rapid, and accurate for the quantitation of total vitamin A in fluid milk containing 2% milk fat. An independent study by Q Laboratories Inc., Cincinnati, OH, under the validation guidelines of AOAC INTERNATIONAL, confirmed these findings.     

Functionalized chloroenamines in aminocyclopropane synthesis - V. synthesis and reactions of aminocyclopropylketones

Conjugated acylated chloroenamines 5A,C were available by chlorination of mixtures of acylated enamines 8A,C/9A,C by NCS at 0°C. Nonconjugated chloroenamines 10Aa and 10Ba could be obtained by NCS-chlorination of the conjugated acylenamines 9A,B at low temperature. Reaction of 5Aa-5Ac,5Ae, 5Af with cyanide produced morpholinocyclopropylketones 11A. In two cases aminofurans 12Ad and 12Ca resulted as products of this reaction. More generally amino-aryl-furans 12 were formed by thermolysis of the aryl-cyclopropyiketones 11. Amino-alkyl-furans as 12Ae and 12Af only could be trapped by a Diels-Alder reaction leading to 16Ae and 16Af. Epoxyenamines 29A,B unexpectedly were produced from the interaction of cyanide with the chloroenamines 10Aa and 10Ba.     

Pre-resonance Raman studies of some mesogens-TB4A,TB7A and TB10A

Pre-resonance Raman spectra of certain liquid crystalline compounds, TB4A, TB7A and TB10A, are reported. The anomaly observed in the pre-resonance Raman spectra in the three compounds was initially explained by the Albrecht-Hutley Model, but its failure leads us to explain the anomalous intensity enhancement mechanism by invoking an interference effect between a weak dipole-forbidden excited state and a nearby strong electronic level via vibrational modes. The presence of a 2¹A_g dipole-forbidden excited state in TB4A and TB10A is deduced after an elaborate discussion of their centro-symmetric structure. The structural difference of TB7A in comparison with TB4A and TB10A is also discussed by taking their X-ray data into consideration.     

Panduratin A inhibits the growth of A549 cells through induction of apoptosis and inhibition of NF-kappaB translocation

In the present study we investigated the effects of panduratin A, isolated from Boesenbergia rotunda, on proliferation and apoptosis in A549 human non-small cell lung cancer cells. Cell proliferation and induction of apoptosis was determined by the real-time cellular analyzer (RTCA), MTT assay and High Content Screening (HCS). The RTCA assay indicated that panduratin A exhibited cytotoxicity, with an IC?? value of 4.4 μg/mL (10.8 μM). Panduratin A arrested cancer cells labeled with bromodeoxyuridine (BrdU) and phospho-Histone H3 in the mitotic phase. The cytotoxic effects of panduratin A were found to be accompanied by a dose-dependent induction of apoptosis, as assessed by DNA condensation, nuclear morphology and intensity, cell permeability, mitochondrial mass/ potential, F-actin and cytochrome c. In addition, treatment with an apoptosis-inducing concentration of panduratin A resulted in significant inhibition of Nuclear Factor-kappa Beta (NF-κB) translocation from cytoplasm to nuclei activated by tumor necrosis factor-alpha (TNF-α), as illustrated by the HCS assay. Our study provides evidence for cell growth inhibition and induction of apoptosis by panduratin A in the A549 cell line, suggesting its therapeutic potential as an NF-κB inhibitor.     

The structure of the chiral Pt531 surface: a combined LEED and DFT study

The structure of the chiral kinked Pt531 surface has been determined by low-energy electron diffraction intensity-versus-energy (LEED-IV) analysis and density functional theory (DFT). Large contractions and expansions of the vertical interlayer distances with respect to the bulk-terminated surface geometry were found for the first six layers (LEED: d12 = 0.44 A, d23 = 0.69 A, d34 = 0.49 A, d45 = 0.95 A, d56 = 0.56 A; DFT: d12 = 0.51 A, d23 = 0.55 A, d34 = 0.74 A, d45 = 0.78 A, d56 = 0.63 A; dbulk = 0.66 A). Energy-dependent cancellations of LEED spots over unusually large energy ranges, up to 100 eV, can be explained by surface roughness and reproduced by applying a model involving 0.25 ML of vacancies and adatoms in the scattering calculations. The agreement between the results from LEED and DFT is not as good as in other cases, which could be due to this roughness of the real surface.     

Preparation and property screening of the solid inclusion complex of norfloxacin with p-sulfonated calix[4]arene

The complexation of norfloxacin (NFLX) by p-sulfonated calix[4]arene (SC4A) in aqueous solution has been studied by fluorescence spectroscopy and 1H NMR spectroscopy. A 1:1 stoichiometry and a 8086 L mol(-1) stability constant of the NFLX-SC4A complex was obtained by spectrofluorometric titrations. The equimolar solid state inclusion complex of NFLX-SC4A was prepared by the co-precipitation method and then characterized by various techniques, including differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD), Fourier-transform infrared analysis (FT-IR) and scanning electron microscopy (SEM). The experimental results of these chemical property screenings confirmed that NFLX and SC4A can form a stable host-guest complex in the solid state, and SC4A appears to function as a complexing and solubilizing agent for NFLX.     

Dual Crosslinking Photo-Switches for Orthogonal Photo-Control of Hybridization Between Serinol Nucleic Acid and RNA

Wavelength-selective photo-regulation by multiple chromophores responding to different wavelengths can expand the variation of photo-manipulating systems. Herein, we report the orthogonal photo-regulation of duplex formation between serinol nucleic acid (SNA) and RNA using light-induced crosslinking reactions mediated by a new photo-reactive nucleobase 8-naphthylvinyladenine (^NVA) and previously described 8-pyrenylvinyladenine (^PVA). An intrastrand crosslink was induced in an SNA strand containing two adjacent ^NVA residues by irradiation with 340–405 nm light; the crosslink was reversed by irradiation with ≤300 nm light. In an SNA strand with adjacent ^NVA and ^PVA residues, an intrastrand crosslink resulted from irradiation with 405–465 nm light that was reversed by irradiation with ≤340 nm light. Intrastrand photo-crosslinking caused severe destabilization of an SNA/RNA duplex, resulting in dissociation to single strands. Cycloreversion resulted in duplex formation. With these ^NVA/^NVA and ^NVA/^PVA photo-switches, four hybridization states of two SNA/RNA duplexes could be orthogonally photo-controlled by irradiation with a suitable wavelength of light.     

三波长分光光度法测定洋葱中蒜氨酸酶的活性

采用三波长分光光度法对洋葱中蒜氨酸酶的活性进行了测定,方法有效地消除了由于背景值及光谱吸收峰不对称给定量分析造成的影响,校正了因干扰组分的吸收光谱具有线性吸收所产生的基线倾斜。分别于波长426nm(λ1)、446nm(λ2)、506nm(λ3)处测定吸光度A1、A2和A3,求ΔA=A2-[(λ2-λ3)A1+(λ1-λ2)A3]/(λ1-λ3)。丙酮酸钠的质量浓度在8.8～44.0mg.L-1之间与ΔA呈线性关系。方法的平均回收率为99.8%,相对标准偏差(n=5)为0.13%。     

Fast protein liquid chromatography of botulinum neurotoxin types A, B and E

Three antigenically different botulinum neurotoxins (NTs, relative molecular mass approximately 150,000), classically distinguished only by specific antisera, were for the first time chromatographically resolved. Mixed NTs eluted from a Mono-Q column in order of types E, A and B, and from Mono-S as B, E and A. Type A and B NTs were successfully chromatographed on the cation-exchange Mono-S column above their isoelectric points. Purification of type A and B NTs by automated liquid chromatography was also accomplished for the first time. Type A, B and E NTs were purified by application on an anion-exchange Mono-Q column, followed by use of a cation-exchange Mono-S column.