时间分辨激光荧光光谱分析方法研究——Ⅰ.铽、镝配合物共存时的分辨原理实验

本文对镝存在时铽的测定,进行了时间分辨激光荧光光谱分析方法的原理性实验。选择Tb、Dy-Sal乙醇溶液体系,测量了Tb~(3+)离子浓度范围为0.01～10μg/ml。Dy~(3+)离子浓度为0.1～100μg/ml范围内的荧光寿命。并得到了此范围内配合物离子浓度与荧光强度具有线性关系的结果。

壳聚糖硫酸酯的制备及其药用价值的研究

壳聚糖是甲壳质脱去乙酰基的产物，本身可生物降解，具有良好的生物相容性，经过磺化引入硫酸根功能团，改变了其理化性质，授予化合物重要生理功能，具有增强机体免疫力，抑制肿瘤，抑制病毒，降糖，降脂，抗凝血，防治血栓、溃疡和肾衰等方面的作用，国内外对其开发十分活跃。本文对壳聚糖硫酸酯衍生物的制备及生物活性进行了比较系统的研究，通过二种方法制备出二个不同含硫量和分子量的样品，分别进行了急性毒性试验和药效试验，结果表明样品毒副作用小，动物对其具有很大耐受性，小鼠i.g和i.p给药的一日最大耐受量分别大于10g/kg和2.5g/kg。该衍生物具有极显著的降血糖和增强免疫作用；在同等剂量下，对防治血栓和抗凝血有一定作用，但不显著；降胆固醇及甘油三酯效果不明显。作为药用的壳聚糖原料应预处理，纯化后原料分子量在20万-30万道尔顿范围，然后采用ClSO_3H/DMF, ClSO_3H/浓 H_2SO_4磺化方法得到硫酸酯衍生物，其 SO_4~(2-)含量分别为 21.6%， 30.5%，取代度分别为 0.44， 0.68。由 IR、 NMR及无素分析证实壳聚糖分子引入了 SO_4~(2-)，取代位点发生以 C_3和 C_6位点。本文对壳聚糖硫酸酯降糖和增强免疫作用机理进行了探讨。壳聚糖硫酸酯具有天然多糖的非细胞毒性特点，可能通过诱导白介素-I、II，活化B细胞、T细胞和巨噬细胞而增强细胞免疫，促进行液免疫；并通过促进胰岛素分泌，提高胰岛素敏感性，增强葡萄糖的代谢利用，从而降低血糖。研究发现，壳聚糖硫酸酯具有剂量依赖生物活性，随首剂量增加，降糖、增强免疫、降胆固醇和甘油三酯、抗凝血和防治血栓形成的作用都增大，随着分子量减小和磺化程度提高，这些药效作用都有所增强。通过本研究工作确定了壳聚糖磺化衍生物进一步开发成为新药的可能性，对深入开发利用甲壳质资源、促进我国海洋药物的发展具有十分重要的意义。

Antioxidant activity of differently regioselective chitosan sulfates in vitro

Differently regioselective chitosan sulfates were prepared according to Hanno Baumann's methods. Their antioxidant potencies were investigated employing various established in vitro systems, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH)/superoxide/hydroxyl radicals scavenging, reducing power, iron ion chelating and total antioxidant activity. All kinds of sulfated chitosans (HCTS, TSCTS, SCTS, TCTS) showed strong inhibitory activity toward superoxide radical by the PMS-NADH system compared to Vc. According to the above-mentioned order their IC50 were 0.012, 0.040, 0.015, 0.022mg/mL, respectively, however, scavenging activity of Vc on superoxide radical was 68.19% at 2.0mg/mL. Scavenging activity of superoxide radical was found to be in the order of HCTS > SCTS > TCTS > TSCTS > Vc. Furthermore, all kinds of sulfated chitosans exhibited strong concentration-dependent inhibition of deoxyribose oxidation. Except for HCTS, others had stronger scavenging activity on hydroxyl radical than Vc. Scavenging effect of TSCTS on 1, 1 -diphenyl-2-picrylhydrazy] radical was little lower than that of BHA, but better than that of others. All kinds of sulfated chitosans were efficient in the reducing power, especially TSCTS. TSCTS and TCTS showed considerable ferrous ion chelating potency. The data obtained in vitro models clearly establish the antioxidant potency of all kinds of sulfated chitosans. These in vitro results suggested the possibility that sulfated chitosans could be effectively employed as ingredient in health or functional food, to alleviate oxidative stress. However, comprehensive studies need to be conducted to ascertain the in vivo safety of sulfated chitosans in experimental animal models. (C) 2004 Elsevier Ltd. All rights reserved.

Analysis of diets of upland buzzards using stable carbon and nitrogen isotopes

We measured the stable carbon and nitrogen isotope ratios for muscles of the upland buzzards (Buteo hemilasius) and their potential food sources, plateau pikas (Ochotona curzoniae), Qinghai voles (Lasiopodomys fuscus), plateau zokors (Myospalax fontanierii), and several passerine bird species at the alpine meadow in Maduo county, Guoluo prefecture of Qinghai province, People's Republic of China, to provide diet information of upland buzzards, highlighting different diet composition of upland buzzards exposed to different locations. The results demonstrated that stable carbon isotope ratios of upland buzzards, passerine birds, plateau pikas, plateau zokors, and Qinghai voles were -24.42 +/- 0.25parts per thousand, -22.89 +/- 1.48parts per thousand, -25.30 +/- 1.47parts per thousand, -25.78 +/- 0.22parts per thousand, and -25.41 +/- 0.01parts per thousand, respectively, and stable nitrogen isotope ratios were 7.89 +/- 0.38parts per thousand, 8.37 +/- 2.05parts per thousand, 5.83 +/- 1.10parts per thousand, 5.23 +/- 0.34parts per thousand, and 8.86 +/- 0.06parts per thousand, respectively. Fractionation of stable carbon and nitrogen isotope ratios between upland buzzards and their food were 1.03parts per thousand and 2.11parts per thousand, respectively. Based on mass balance principle of stable isotopes and the Euclidean distance mixing model, upland buzzards depended mainly on plateau pikas as food (74.56%). Plateau zokors, Qinghai voles, and passerine birds only contributed a small proportion (25.44%) to diets of upland buzzards. The results were closely accordant with analyses of stomach contents and food pellets, which firmly supported the feasibility of using stable carbon and nitrogen isotope ratios to investigate diet information of upland buzzards. Another study based on stable carbon isotopes showed that upland buzzards living in the Haibei prefecture (another prefecture located in the southeast Qinghai province) mainly preyed on passerine birds (64.96% or more) as food supply. We were alarmed by the preliminary results that widespread poisoning activities of small mammals could reshape the food composition of upland buzzards, influencing the stability and sustainability of the alpine meadow. Bio-control on rodent pests should be carried out rather than the chemical measures.

中国黄土高原洛川剖面 630 kyr 以来的孢粉记录

It is known that global climate changed from the early Tertiary “Green House” to the Quaternary “Ice House” of cyclic glacial-interglacial climatic changes. Since the middle Pleistocene, the climate cycles changed from 40 kyr to 100 kyr, and the amplitudes of climatic fluctuations increased significantly. Therefore, it is important to study the climate changes since the middle Pleistocene. The loess-paleosol sequence in China is considered as one of the most continuous continental records of the last 2.58 Ma. Paleoclimatic and environmental changes have been widely extracted through various climatic parameters. However, the history of paleovegetation on the Loess Plateau still remains unclear. Did an extensive broadleaf forest ever exist on the Loess Plateau? Pollen preserved in the loess and paleosol provides a direct record for vegetation and paleoenvironmental change on the Plateau. However, because it is difficult to extract sufficient pollen grains from loess, the pollen record since the middle Pleistocene especially in the central part of the Chinese Loess Plateau has not been well studied. So we preliminarily focus on the palynological records of the loess-paleosol sequence spanning the last 630 kyr at Luochuan and aim to understand the evolution of vegetation and climate change on the Chinese Loess Plateau. The main results and conclusions are as follows: 1. The palynological results show that the grassland has been a dominant vegetation in the Luochuan area since 630 kyr, even during the intervals of relatively warm and wet climatic conditions. 2. The pollen concentration of Luochuan section sharply decreases from the bottom of S1 to downward depth. This decrease can be attributed to depositional environment rather than climate change. In loess, not only oxidation, but also the PH of deposits and bacteria or fungi have been able to degrade sporopollenin. 3. The paleoclimatic condition during S4 stage, characterized with warmer condition during the early stage, was warmer and wetter than that during S5 in Luochuan area. Paleoclimate was warmer and wetter during the early stage of S5 and became colder and drier later. The special pedogenic features of S5-I can be attributed to a prolonged pedogenic duration rather than a warm-wet climate. 4. Evidence from pollen assemblage suggests that the Holocene vegetation has been affected by human impacts, especially after the Yangshao Culture. 5. The present steppe environment on the loess plateau is mainly due to natural conditions. Temperature, seasonal precipitation and soil structure are three important factors which control the vegetation type. 6. The vegetation on the loess plateau is characterized with zonal or azonal distribution. So local conditions should be taken into account when recover natural vegetation. Finally, the restoration and reconstruction of ecosystem on the loess plateau area should be focused on planting grassland rather than forests.