尿素与甲醛加成及缩聚产物~(13)C NMR研究

合成并研究了几种尿素与甲醛的加成、缩聚产物结构，使用高分辨１３Ｃ核磁共振仪（ＤＲＸ－５００）确定了几种典型结构的化学位移并对化学位移的变化规律展开讨论；研究了一种脲醛树脂合成中间产物及最终液体树脂的结构，指定了各吸收峰的归属；结合模型化合物研究结果并参考文献，给出了脲醛树脂各结构单元的化学位移。     

CNMR定量分析

采用13C NMR定量分析了由选定碱-酸-碱工艺所合成的E1级胶合板用脲醛树脂.结果 表明:在初始碱性阶段有70.27 %的甲醛分子转化成了羟甲基脲,24.83 %的甲醛分子转化成了亚甲基醚键.在随后的酸性缩聚阶段中,64 %的羟甲基脲发生断裂,放出甲醛,缩聚成亚甲基键及亚甲基醚键.在酸性阶段加入的第二批尿素与树脂中的游离甲醛形成羟甲基脲.超过一半的亚甲基醚键在最后的碱性保温阶段发生分解,并与此时加入的第三批尿素生成羟甲基脲.     

固体核磁共振法对低甲醛释放脲醛树脂化学结构的研究

在采用液体核磁对3种低甲醛释放脲醛树脂化学构造进行分析的基础上,利用13CCP/MASNMR对脲醛树脂固化产物的化学结构进行了研究.结果表明,不同固化体系下,3种低甲醛释放脲醛树脂胶黏剂的固化历程不同,固化后树脂的结构有所差别.不添加固化剂时,脲醛树脂的固化交联反应程度低,固化产物中羟甲基含量高,甲醛释放量也随之增加.加入固化剂后,促进了羟甲基的固化交联反应,脲醛树脂固化产物中羟甲基含量普遍降低.3种固化体系下,UF-3羟甲基含量最高;在氯化铵为固化剂的条件下,UF-2羟甲基含量最低,为0.0582;不添加固化剂和复合固化体系条件下,UF-1羟甲基含量最低,分别为0.0784和0.0713.不同固化体系对不同种类脲醛树脂的固化效果不同,固化后树脂的结构不同,其力学性能和甲醛释放能力也不同.     

“I-214杨”心材、边材木质素的红外光谱、质子和碳-13核磁共振波谱特征研究

对从杨树心、边材提取的磨木木质素进行了元素分析和红外光谱（FTIR）质子和碳－13核磁共振波谱（^1H,^13C NMR)等化学特征研究。研究结果表明：杨树心、边材木质素的经验式分别为C9H7．16O2．38（OCH3）1．99和C9H8．61O2．73（OCH3）1．33。心材木质素甲氧基含量28．16％,比边材高8．73％。两种木质素均具有典型阔叶材的特征,化学结构类型基本一致,碳骨架结构基本相同,但化学官能团和键型的组成上存在差异。     

Isolation and NMR spectra of syringaresinol-beta-D-glucoside from Cressa cretica

The isolation, (1)H-NMR and revised (13)C-NMR assignments of syringaresinol-beta-D-glucoside from Cressa cretica are reported.     

Analysis of the structure of lignin-carbohydrate complexes by the specific13C tracer method

In the present study the specifically¹³C-enriched lignin precursors of biosynthesis (i.e., coniferin-[side chain–¹³C], coniferin-[side chain-–¹³C] and coniferin-[side chain-–¹³C]) were synthesized and administered exogeneously to ginkgo shoots (Ginkgo biloba L.) to obtain¹³C-enriched lignin-carbohydrate complexes (LCCs). The specifically¹³C-enriched LCCs were isolated from the newly formed xylem of ginkgo shoots administered with the¹³C-enriched precursors and degraded by enzymes. Lignin-rich fractions, so called enzyme-degraded LCCs (EDLCCs), were obtained. By determining their¹³C-NMR spectra, information related to the chemical structure of lignin building units and linkages between phenylpropane units of lignin and carbohydrates were obtained. It was found that these precursors were incorporated in natural lignin successfully. Three lignin-carbohydrates linkages (i.e., ether type, ester type, ketal type) were found at the C -position of the side chain of phenylpropane units in ginkgo LCC. No lignin-carbohydrate bond at the C- or C-position of the lignin side chain was observed in the¹³C-NMR spectra of the¹³C-enriched LCCs. This fact indicates that a specific¹³C tracer technique can be useful in NMR study of the chemical structure of LCCs.Part of this paper was presented at the 5th Pacific Polymer Conference, Kyongju, Korea, October 1997     

C2H2-reduction byErythrina poeppigiana in a Costa Rican coffee plantation

Acetylene reduction activity by root nodules of the legumeErythrina poeppigiana, growing as shade tree in a Costa Rican coffee plantation, was estimated. The mean activity found was 15.7 nmole C₂H₄ · mg (dry weight)^–1 · h^–1. Root nodules collected at different distances from theErythrina stem showed the same activity per dry weight unit. However, as the biomass of the nodules was highest near the stem, was the acetylene reduction activity (expressed per soil volume) maximal near theErythrina stem and declined with distance.     

外施H2O2对黄瓜幼苗抗低温胁迫的影响

以"津研7号"和"津春4号"黄瓜幼苗为材料,在其生长期外施不同浓度的H2O2,研究了H2O2对黄瓜幼苗抗低温胁迫的影响.结果表明:黄瓜幼苗经低温胁迫后,其电导率和丙二醛含量急剧上升,而过氧化物酶活性和可溶性蛋白含量明显降低;与对照相比,外施H2O2能提高其过氧化物酶活性,降低膜渗漏率,增加可溶性蛋白含量,减缓膜脂过氧化作用,从而提高黄瓜幼苗的抗低温胁迫能力,其中以10 mmol.L-1的H2O2处理效果最为明显.     

双氧水处理对白蜡种子发芽的影响

在实验室进行了双氧水不同浓度和处理时间对白蜡种子发芽的影响研究,结果表明不同处理浓度（0％～4.0％）白蜡种子发芽率为64％～79％,有随浓度升高而增加的趋势,其中双氧水浓度为3.5％的效果最好,极显著高于其他处理（p＜0.01）,其他处理之间差异不显著（p＞0.05）;在双氧水处理浓度3.0％时,浸种12 h的发芽率为71％,极显著高于浸种24h时的42％发芽率（p＜0.01）.     

云南13种乡土绿化树种对SO2、NO2气体反应的研究

采用人工模拟熏气的方法,研究了13种云南乡土绿化树种对城市SO2、NO2有害气体的反应.结果表明云南红豆杉、长梗润楠、翠柏、滇润楠、麻栗坡含笑、南亚含笑、山玉兰对SO2气体的抗性弱,而云南含笑、脉叶虎皮楠、川滇三角枫对SO2气体的抗性最强,灯台树、川滇三角枫净化SO2的能力较强,其净化量分别为300mg·kg-1、700 mg·kg-1.NO2浓度为1.0 mg·m-3时,长梗润楠、云南含笑、云南拟单性木兰、云南红豆杉、麻栗坡含笑、灯台树叶片的N净化量依次为2 000 mg·kg-1、1 100 mg·kg-1、1 700 mg·kg-1、2 300 mg·kg-1、1 200 mg·kg-1、13 100 mg·kg-1.经综合比较川滇三角枫对SO2气体具有较好的抗性和净化能力,而对NO2气体具有较好的抗性;云南含笑、云南拟单性木兰、脉叶虎皮楠等树种对SO2、NO2气体具有较好的抗性和净化能力.     

核磁共振光谱和X射线光电子能谱对纤维低聚糖的分析

1H-1HCOSY和13C-1HHSQC谱对通过Bio-GelP-2柱(2.5cm×125cm)分离制备的纤维三糖、纤维四糖和纤维五糖进行分析。结果表明,在水溶液中纤维低聚糖还原末端C1位α构型与β构型之比(α/β)随聚合度增大而减小,纤维三糖主要是α构型(α/β,0.52),而纤维四糖和纤维五糖主要是β构型(α/β,分别是0.34和0.25)。X射线光电子能谱(XPS)分析表明纤维低聚糖的C1s主要有2种电子结合能,分别为284.8(C1s1,C—O)和286.1eV(C1s2,O—C—O),C1s1与C1s2之比(C1s1/C1s2)随聚合度增大而增大。     

下的降解

对木质素磺酸盐在紫外光/双氧水(UV/H2O2)体系下的降解过程进行了研究,通过对比处理前后木质素磺酸盐溶液的紫外可见光谱、凝胶渗透色谱(GPC)谱图、红外光谱谱图、1H NMR谱图及溶液化学耗氧量(COD)的变化对其降解过程进行了跟踪和讨论。此外,通过对木质素的模型化合物——愈创木酚降解的研究,推测了降解中苯环的开环过程。实验结果表明,木质素磺酸盐在UV/H2O2体系处理下能够发生降解,降解过程中首先生成一些中间产物,随着反应时间的加长,最终能够降解成CO2、H2O等小分子化合物。     

Isolation and identification of degradation products of salvianolic acid A by NMR and LC-MS

Salvianolic acid A was subjected to thermal degradation condition in distilled water at 90 °C. Four degradation products, including two novel compounds (1, 2) and two known ones (5, 6), were isolated by reverse-phase semi-preparative liquid chromatography and identified on the basis of NMR and MS data. Other two degradation products (3, 4) were determined by LC-MS analysis.     

沙柳及柠条灌木材液化产物的核磁共振谱分析

以苯酚为液化剂、硫酸为催化剂的高温油浴加热下液化沙柳、柠条.采用核磁共振仪分别测试了二者液化产物的结构并进行比较分析,结果显示:沙柳、柠条在酸性条件下液化过程中,同时进行着降解、缩聚反应,液化产物主要生成了β-D-葡萄糖和松柏醇芳香核质子以及愈创木基型木质素结构;从1〖KG-*9〗HNMR图谱看出:沙柳液化物峰面积中所含平均质子的数量要多于柠条液化物,而13CNMR分析中,二者液化物的化学位移位置变化基本一致,只是沙柳液化物的谱线强度要比柠条液化物的谱线强度稍大一些.      

稳定性同位素技术在森林生态系统碳水通量组分区分中的应用

生态系统碳水循环过程中的同位素分馏效应,为区分生态系统净碳交换过程中光合和呼吸通量,蒸散通量中植物蒸腾和土壤蒸发提供了理论依据.本文综述了稳定性同位素技术在这一领域的应用进展.研究结果显示,此方法切实可行,为进一步解释森林生态系统过程提供了广阔的前景.但由于森林生态系统结构复杂,不确定性因素多,国内外研究还处于尝试阶段.该方法在森林生态系统应用中还存在诸如Keeling图技术和涡度相关技术的假设条件难以满足等问题,期待今后在技术和理论上的突破.     

H2O2介导真菌诱导子促进白桦酯醇积累

以产白桦酯醇的白桦悬浮细胞系为试材,利用药理学试验,结合高效液相色谱和荧光显微镜技术,探讨过氧化氢(H2O2)在拟茎点霉属真菌诱导子促进白桦酯醇积累中的作用.结果表明:外源H2O2降低了细胞的活力和干质量的积累量,却提高了白桦酯醇的含量.其中,1 mmol· L-1H2O2处理12 h,白桦酯醇的含量比对照增加89.45％,0.1 mmol·L-1H2O2处理24 h,白桦酯醇的含量比对照增加73.72％.真菌诱导子促进了白桦悬浮细胞中H2O2和白桦酯醇的生成,在处理24 h时,分别比对照增加391.67％和185.22％.H2O2的清除剂过氧化氢酶减弱真菌诱导子对H2O2和白桦酯醇的诱导效应.由上述结果初步推断,H2O2参与了真菌诱导子诱导白桦酯醇积累的过程.     

Inhibitory effect of tanshinones on rat CYP3A2 and CYP2C11 activity and its structure-activity relationship

This study investigated the effect of tanshinones on rat liver microsomal CYP3A2 and 2C11 activity and explored the structure-activity relationship of tanshinones with CYP3A activity. Cryptotanshinone, tanshinone I and tanshinone IIA were competitive CYP3A2 inhibitors (K_i = 199-243 μM) and CYP2C11 inhibitors (K_i = 91-118 μM). Dihydrotanshinone was not only a noncompetitive inhibitor of CYP3A2 (K_i = 110 μM), but also a competitive CYP2C11 inhibitor (K_i = 55 μM). The structural difference between dihydrotanshinone and tanshinone I at C-15 position of furan ring resulted in the different modes of inhibition on CYP3A activity.     

左旋海松酸丁醇胺盐光敏氧化反应的研究

以亚甲基蓝为光敏剂,研究了左旋海松酸丁醇胺盐(简称ASL)在95%乙醇中的光敏氧化反应。结果表明,ASL经光敏氧化反应生成左旋海松酸环过氧化物丁醇胺盐(简称ASLP);由于溶解度低,小于1 g.(100 mL)-1,以及对含有碱性基团的亚甲基蓝的弱吸附作用,ASLP在反应过程自动结晶析出,分离与纯化方法简单易行;光敏剂、反应溶剂无需任何处理,可以直接回收使用。     

Nitrogenase activity (C2H2 reduction) in the forest floor of a Pinus elliottii plantation following superphosphate addition and prescribed burning

The C₂H₂ reduction method was used on eight occasions between January 1983 and January 1984 to measure the effects of adding superphosphate (60 kg P ha⁻¹ applied in September 1979) and of prescribed burning (May 1981) on nitrogenase activity in the forest floor of an 18 year old Pinus elliottii plantation in southeast Queensland.Averaged over sampling days, superphosphate increased nitrogenase activity in the forest floor 4.0-fold in the unburnt plots and 2.0-fold in burnt plots. In the absence of superphosphate, burning increased activity 3-fold but in plots receiving superphosphate a response to burning was seldom evident. The responses were attributed to increased nutrient availability. Nitrogenase activity was highest in the F1 layer (weathered needles in the centre of the forest floor) and lowest in the L layer (recently fallen needles). Moisture content has a strong effect on forest floor nitrogenase activity and, in laboratory dried material, activity increased most rapidly for moisture contents between 80 and 170%.Mean nitrogenase activity in the forest floor on individual sampling days ranged from 3 nmol C₂H₄ g⁻¹ (L layer, control treatment) to 233 nmol C₂H₄ day⁻¹ (F1 layer, combined refertilized and burnt treatment). Activity was also detected in dead wood, female cones, thinning debris, soil (0–5 cm) and roots, but was negligible in bark and green needles.