土壤腐殖质的分析化学研究进展

对土壤腐殖质的分析化学研究进展作了综述。具体包含如下几个方面的内容；土壤腐殖质的组成和结构的研究，土壤腐殖质的起源和形成的研究，土壤腐殖质与土壤中有机，无机物质的相互作用的研究以及有机物料的分解，转化及其对腐殖质影响的研究，同时，对土壤腐殖质的研究中有待进一步用分析化学方法解决的几个问题进行了探讨。     

基团的电子效应与单取代苯对位^1H,^13C的化学位移

基团的电子效应与单取代苯对位１Ｈ、１３Ｃ的化学位移＊韩长日冯娇杨钟照平（海南师范学院化学系海口５７１１５８）关键词１Ｈ的化学位移１３Ｃ的化学位移基团电负性共轭效应引言在１Ｈ、１３Ｃ核磁共振谱中，化学位移值的大小主要取决于屏蔽作用的大小，而屏蔽作用的大...     

一种计算基团电负性的简单方法

基团(取代基)电负性在研究复杂分子特别是有机化合物的结构和性质中是一个重要参数。人们在这方面已作了许多工作,文献报道的基团电负性值不少于十套。但这些方法大都太繁,公式复杂且参数较多,不便运用。本文试以核磁共振谱的质子化学位移值为依据,建立一个简单的计算公式。人们熟知,核磁共振谱中的质子化学位移与围绕质子的电子密度相关,而质子周围的电子密度又与邻近的取代基的基团电负性紧密相关。电负性大的基团     

以去氢弯孢霉素NMR结构解析讲授本科生波谱分析课程

以去氢弯孢霉素核磁共振波谱(NMR)解析为例,讲授本科化学和药学相关专业波谱分析课程NMR解析。去氢弯孢霉素结构包含苯环、双键、酚羟基、羰基和酯基等常见基团,NMR信号几乎无重叠、辨识度高,非常适合作为核磁共振波谱结构解析中化学位移、耦合常数和二维核磁共振波谱的授课内容。     

模板分子TMEDA成CF—3及ZSM—39沸石笼中的位置及其与骨…

用ＸＲＤ、ＦＴＩＲ、ＴＧ－ＤＴＡ、＾１３Ｃ魔角固体核磁共振表征用四甲基乙基二胺（ＴＭＥＤＡ）为结构异向剂合成的高硅沸石ＣＦ－３及ＺＳＭ－３９．ＴＭＥＤＡ不同基团的＾１３Ｃ化学位移，共振峰相对强度在交叉极化（ＣＰ）及高功率去偶（ＨＰＤＥＣ）核磁共振谱中的变化，揭示出模板分子在尺寸不同的沸石笼中的位置、运动状态及其与骨架的相互作用。在ＺＳＭ－３９沸石中的ＴＭＥＤＡ分子，它的－Ｃ２Ｈ４－基团＾１３Ｃ共振     

高分辨核磁共振的一些进展

核磁共振作为有机分析主要工具之一,帮助鉴定了数十万种以上化合物的结构,而且随着实验技术的进步,与核磁共振有关技术的发展,用途也更加广泛,除在有机化学、高分子化学方面应用以外还深入到其他几乎所有的化学领域。本文介绍超导高磁场核磁共振的主要特点和当前核磁共振技术中最重要的脉冲傅立叶变换核磁共振的简单原理,以及弛豫时间的测定及其用途。由于应用傅立叶变换原理,能分别测出化合物中各基团的弛豫时间,使弛豫时间亦能提供有关分子结构的信息。因此在有机化学、生物化学等方面应用也有重要的意义。     

一种新型天然脲酶抑制剂曲霉素的结构与抑酶效应

从赭曲霉（Aspergillusochraoeus）代谢产物中获得一种新型的脲酶抑制剂曲霉素，经核磁共振，质谱仪等分析，推导出该化学结构为3－（1′，2′-环氧（丙基）－5，6-双氢-5-羟基-吡喃-正酮。通过X-射线衍射测定进一步肯定了上述结论。它是一种白色晶体，易溶于水和乙酸乙酯，对热较稳定，对刀豆脲酶和土壤脉酶有抑制作用，其抑制作用随抑制剂浓度增加而增强。抑制类型为非竞争抑制，Ki为1.3×10-3mol/L其抑制机理与该物质结构中的-C=O，-OH，-COOH基团有关。     

腐植酸高吸水性树脂研究进展

腐植酸（HA）是土壤腐殖质的主要成分,含有多种功能基团。随着HA基础和应用研究的不断深入,将具有反应活性和生物活性的HA引入到高吸水性树脂中,既能发挥HA改良土壤、增效化肥、刺激生长、增强抗逆和改善品质的功效,又可改善高吸水性树脂的吸水和耐盐性能,同时大幅度降低高吸水性树脂的制备成本。本文综述了近年来HA高吸水性树脂的...     

环氧化天然橡胶中环氧基团分布情况的研究

通过在胶乳状态下原位生成过氧甲酸制备环氧化天然橡胶（ENR），采用傅里叶变换红外光谱（FRIR）对环氧化天然橡胶的结构进行表征，核磁共振谱仪（NMR）和差示扫描量热仪（DSC）对环氧基团的分布进行了研究，结果表明，过氧甲酸能迅速地渗透到橡胶粒子的内部，使环氧化基团分布在整个橡胶粒子上，环氧基团在ENR分子链上是无规分布...     

点击化学法制备含有肉桂酸酯基团的线性聚合物的研究

利用点击化学方法合成了一种侧链上含有肉桂酸酯基团的线性聚合物,利用核磁共振(1H NMR)、红外光谱(FTIR)、凝胶渗透色谱(GPC)和示差扫描量热分析(DSC)等方法对该聚合物的结构和性能进行了表征。DSC谱图显示,在170℃附近出现一个明显的放热峰,通过进一步的实验证明,该放热峰是由聚合物侧链上残余的叠氮基团与肉桂酸酯基团上的碳碳双键发生反应引起的。另外,实验证明,通过稀盐酸处理,可以消除聚合物中残余的叠氮基团。     

Recovering Invisible Signals by Two‐Field NMR Spectroscopy

Nuclear magnetic resonance (NMR) studies have benefited tremendously from the steady increase in the strength of magnetic fields. Spectacular improvements in both sensitivity and resolution have enabled the investigation of molecular systems of rising complexity. At very high fields, this progress may be jeopardized by line broadening, which is due to chemical exchange or relaxation by chemical shift anisotropy. In this work, we introduce a two‐field NMR spectrometer designed for both excitation and observation of nuclear spins in two distinct magnetic fields in a single experiment. NMR spectra of several small molecules as well as a protein were obtained, with two dimensions acquired at vastly different magnetic fields. Resonances of exchanging groups that are broadened beyond recognition at high field can be sharpened to narrow peaks in the low‐field dimension. Two‐field NMR spectroscopy enables the measurement of chemical shifts at optimal fields and the study of molecular systems that suffer from internal dynamics, and opens new avenues for NMR spectroscopy at very high magnetic fields.     

环己烷催化氧化制取顺酐和醋酸的催化剂研究

为研究气态环己烷催化氧化制取顺酐及醋酸的新反应，采取不同的方法制备了系列固体VPO催化剂.借助XRD、FT-IR对催化剂进行了主体晶相确定，用氧化还原滴定方法测定了不同晶相催化剂中钒的平均氧化数.结合催化反应的活性评价，发现催化剂主体晶相、结晶度、活化气氛和催化剂的V4＋/V5＋比均对目标反应的催化活性产生影响，5种催化剂中以(VO)2P2O7晶相催化剂的活性为最高.     

Atomic Properties of Amino Acids: Computed Atom Types as a Guide for Future Force‐Field Design

The quantum chemical topology (QCT) is able to propose atom types by direct computation rather than by chemical intuition. In previous work, molecular electron densities of 20 amino acids and smaller derived molecules were partitioned into a set of 760 topological atoms. Each atom was characterised by seven atomic properties and subjected to cluster analysis element by element, that is, C, H, O, N, and S. From the respective dendrograms, 21 carbon atom types were distinguished, 7 hydrogen, 2 nitrogen, 6 oxygen, and 6 sulfur atom types. Herein, we contrast the QCT atom types with those of the assisted model building with energy refinement (AMBER) force field. We conclude that in spite of fair agreement between QCT and AMBER atom types, the latter are sometimes underdifferentiated and sometimes overdifferentiated. In summary, we suggest that QCT is a useful guide in designing new force fields or improving existing ones. The computational origin of QCT atom types makes their determination unbiased compared to atom type determination by chemical intuition and a priori assumptions. We provide a list of specific recommendations.     

Flow Field Induced Steady Alignment of Oxidized Multi-walled Carbon Nanotubes

The steady ordered micro-ribbons of oxidized multi-walled carbon nanotubes (MWNTs) were obtained through micro-aperture PTFE membrane by vacuum filtration. After treatment by mixture of concentrated nitric acid and sulfuric acid, the surface functional groups modified MWNTs can be easily dispersed to form a homogeneous suspension. It is found that the steady micro-ribbons existed in the films obtained by vacuum filtration of the suspension. The filtration formed steady flow field and induced steady alignment of oxidized MWNTs. The chemical treatment of MWNTs forming strong interaction between MWNTs is necessity to keep steady of the micro-ribbons microstructure.     

用于电渗控制的新型毛细管电泳装置

提出了一种可利用径向电场控制电渗的新型毛细管电泳装置，着重讨论了其工作原理，电渗控制方法及相关结果。该装置不仅能方便地实现电渗的电场控制，而且通过略加改进，还能与商品仪器兼容。     

Field Sweep Spin Decoupling of Weakly Coupled Unsymmetrical Three-Spin System

Proton magnetic resonance spectrum of 25% (volume) methyl 2,3-dibromopropionate in benzene exhibits a typical ABC pattern in which the four strong lines from each nucleus can be immediately recognized. The assignment of spectral lines and the determination of energy-level diagram were thus straightforward. Field-sweep spin decoupling experiment with respect to the outer transition-square of the sample was found to be in complete analogy with two-spin AX system. However, spin decoupling with respect to the inner transition-square reveals a weak satellite line on each side of the decoupled A (or C) signal. These weak satellite lines are found to be due to J_AB (or J_BC) and may prove to be useful for the direct determination of J_AB and J_BC.     

MEDIATION OF LIGHT-INDUCED CHANGES IN PINEAL RECEPTOR AND SUPPORTING CELL NUCLEI AND NUCLEOLI IN STEELHEAD TROUT (SALMO GAIRDNERI)

Abstract— Mediation of the chronic effects of differences in environmental illumination on pineal photoreceptor and adjacent supporting cells was studied in two experiments using larval trout. Experiment 1 had 7 groups exposed to controlled lighting conditions for 14 months: (1) constant darkness (DD); (2) natural photocycles (LD) followed by constant light (LL); (3) natural photocycles (LD); (4) LD fluorescent light; (5) LD blue (400–525nm) light; (6) LD green (500–612nm) light; and (7) LD red (600–750 nm) light. In Experiment II the fish were exposed to LL for 27–28 days, following 10 months in DD and one of five surgical manipulations: (1) pineal masked; (2) pineal sham-masked; (3) blinded; (4) blinded + pineal masked; (5) blinded + pineal sham masked.
Nuclei and nucleoli of pineal receptor and supporting cells were largest in fish raised in DD. LL or LD cycles, and light of either narrow or broad spectral range, were not notably different in their chronic effects on receptor cell nuclei and nucleoli. However, supporting cell nuclei and nucleoli were smallest in LL. Blinding and pineal masking demonstrated that: (1) pineal receptor cell nuclei and nucleoli were affected by chronic incident light in the pineal region but not by photic or visual influences via the lateral eyes; and conversely, (2) pineal supporting cell nuclei and nucleoli were affected by chronic photic input only via the lateral eyes. The results suggest the possible presence of a cellular comparator system in which photic inputs from lateral eyes and pineal affect separately and respectively the adjacent supporting and receptor cells of the pineal organ.     

Selective surface reactions for Janus ORMOSIL particles with multiple functional groups using an ordered monolayer film at liquid-liquid interface

Monodispersed, submicron-sized Janus ORMOSIL particles with multiple functional groups were prepared by the selective surface reaction of a monolayer film formed at a hexane-water interface. A well-ordered monolayer film was obtained by self-assembly of ORMOSIL particles with multiple functional groups at hexane-water interface. The photopolymerization of an ordered monolayer containing ORMOSIL particles yields a rigid film strong enough to maintain its integrity for transfer and further chemical reaction. The chemical reaction of this ordered film with organic and inorganic functional groups produced Janus ORMOSIL particles with multiple functional groups. The morphologies, structures, and chemical compositions of monolayer films and Janus ORMOSIL particles were characterized by FT-IR, solid state NMR, X-ray diffraction (XRD), optical microscopy (OM), electron microscopies (SEM and TEM), and confocal laser scanning microscopy.     

A Benzophenone‐Based Photocaging Strategy for the N7 Position of Guanosine

Selective modification of nucleobases with photolabile caging groups enables the study and control of processes and interactions of nucleic acids. Numerous positions on nucleobases have been targeted, but all involve formal substitution of a hydrogen atom with a photocaging group. Nature, however, also uses ring‐nitrogen methylation, such as m⁷G and m¹A, to change the electronic structure and properties of RNA and control biomolecular interactions essential for translation and turnover. We report that aryl ketones such as benzophenone and α‐hydroxyalkyl ketone are photolabile caging groups if installed at the N7 position of guanosine or the N1 position of adenosine. Common photocaging groups derived from the ortho‐nitrobenzyl moiety were not suitable. Both chemical and enzymatic methods for site‐specific modification of N7G in nucleosides, dinucleotides, and RNA were developed, thereby opening the door to studying the molecular interactions of m⁷G and m¹A with spatiotemporal control.     

The Stability of Precipitation Samples under Field Conditions

Abstract

Eight wet-only samplers. placed in one location were used to sample precipitation. Subsamples were taken from the sample bottles directly after the precipitation event and at regular intervals up to a period of 2100 hours and analysed, while the samples stayed in the samplers under field conditions.

Outliers were deleted by means of conventional statistical techniques. The resulting data base was tested by means of the F-test for consistency and for changes in the chemical composition of precipitation samples directly after sampling or after an extended stay under field conditions. Eighty-one percent of the samples showed consistent results and no clear indication of chemical changes was found.

Regression analysis indicated that the uncertainties for samples analysed after 1 week are less than 5% generally for the bulk elements and less than 14% for the trace elements. After a period of 400 hours the uncertainties for the buld elements increase to a level of 5–10% and 5–30% for the trace elements.

Contamination, as a result of handling the samples to obtain subsamples, seems the main cause for the increase of the concentrations which was observed.

Contamination during sample pretreatment and analysis in the laboratory is probably of minor importance.