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甲壳质及壳聚糖的硫酸酯化反应是其化学修饰中最吸引人的研究内容之一。由于它们与肝素有相似骨架， 经硫酸酯化，引入-NHSO3H， - CH2OSO3H - OSO3H， COOH，-CH2COOH基团后得到甲壳质(壳聚糖)类肝素药物，显示出抗栓、抗凝血性能(李鹏程等，1998；曾宪放等，1992；Proeyanat et al.，2002)；如Muzzarelli(1985)早已预见并证实其抗凝血活性；莫斯科血液研究中心病理药理系止血组的研究人员也证明了壳聚糖硫酸酯具有抗凝血活性，他们将肝素与壳聚糖硫酸酯以1∶1的比例给家兔静脉注射各0.5mg/kg，与单纯用肝素1mg/kg对照组比较，其抗凝血效应基本接近，但对照组有出血副作用，而试验组无副作用，可以证明壳聚糖硫酸酯具有既抗凝血又止血的双重调节作用；Tokura等(1994)证实分子质量大小和脱乙酰度不同对磺化产物的抗凝血活力有影响，样品分子质量26000 Da的活性最高，脱乙酰度70%比45%的抗凝血活性更强，脱乙酰度为95%的壳聚糖磺化后抗凝血活性最弱。在中国这方面的研究相对较少，特别是分子中含硫的多寡对生物活性的影响还未见报道。本文作者就壳聚糖的磺化产物对大鼠抗栓、抗凝血进行了研究，表明壳聚糖硫酸酯具有一定的抗栓、抗凝血效果，且具有一定的量效关系，这对今后该方面的进一步研究提供了科学理论依据。 相似文献
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以灰树花发酵菌丝体水不溶性多糖GF4A为原料,以三氧化硫三甲胺盐(SO3·Me3N)为酯化试剂,探讨了GF4A的硫酸酯化工艺.实验结果表明,当三氧化硫与GF4A中单糖摩尔比为5.8∶1、反应温度为80 ℃、反应时间6 h时,所得酯化产物(SGF4A)水溶性好、产率高.该产物硫酸酯取代度为1.6, 相对分子质量为88 kD.通过红外光谱及核磁共振碳谱分析表明,糖残基中所有C-6羟基以及部分C-4和C-2位羟基被酯化.体外实验表明,SGF4A具有较好的抗凝活性. 相似文献
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应用分光光度法测定海水中碳水化合物含量的反应试剂有苯酚、葸酮、苔黑酚、N-乙基咔唑和左旋—色氨酸等，其中常用的是苯酚硫酸法。由于该法的重现性较差，近年来已作了一些改进。在《海水分析方法》一书中，Josefsson指出左旋—色氨酸在硼酸存在下是一个与碳水化合物反应的理想试剂，因它与所有的单糖生成的紫色化合物均有相似的吸收光谱，并提出可用手工操作快速测定其总量。 相似文献
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以吩嗪硫酸甲酯-NADH为超氧阴离子自由基(O_2~(·-))产生、检测体系和EDTANa_2-Fe(Ⅱ)-H_2O_2为羟自由基(~·OH)产生、检测体系,对壳聚糖硫酸酯铜、锌配合物和不同分子质量壳聚糖进行了抗O_2~(·-)和~·OH自由基的活性研究.结果表明,壳聚糖硫酸酯金属配合物对于O_2~(·-)自由基的清除能力明显高于壳聚糖,在质量浓度为0.025 g/L时,壳聚糖硫酸酯铜配合物对O_2~(·-)自由基的清除能力达到94.18%,壳聚糖硫酸酯锌配合物达到93.19%;壳聚糖硫酸酯铜、锌配合物对~·OH自由基的清除能力(67.39%、60.46%)低于相同分子质量的壳聚糖(88.06%),而高于高分子质量壳聚糖761 ku(18.71%);壳聚糖分子质量大小对O_2~(·-)和~·OH自由基的清除能力有较大影响,质量浓度为1.6 g/L壳聚糖分子质量为20 ku时,对O_2~(·-)清除率达54.69%,而分子质量在761 ku时,对O_2~(·-)清除率仅为35.50%;各样品对O_2~(·-)和~·OH自由基的清除能力均随着质量浓度的增加而上升,壳聚糖硫酸酯铜、锌配合物在相当低的浓度下(0.025 g/L)就可以达到明显清除O_2~(·-)自由基的效果(≥90%). 相似文献
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甲壳素是一种天然高分子多糖，具有与纤维素相近的骨架结构，其资源丰富，用途广泛(方波，1998)。但由于分子内和分子间存在很强的氢键作用力，因而不能熔融，也不溶于普通溶剂(如水、乙醇等)(董炎明等，2002)，实际应用中较多的是其部分或全部脱乙酰化产物——壳聚糖。壳聚糖虽然可以溶于酸性水溶液，但不能直接溶于水中，且在酸性水溶液中不稳定，也不溶于一般的有机溶剂，这在很大程度上限制了它的应用(董炎明等，2002)。所以，水溶性壳聚糖衍生物的研制正成为一个新的研究方向。壳聚糖分子中C2位上的-NH2，C3、C6位上的-OH，均具有较强的反应活性，在适当条件下可进行多种化学修饰，如酰基化、羧烷基化、硫酸酯化、烷基化、羟烷基化及氰烷基化等。引入上述功能性基团，可增加壳聚糖的溶解性和功能性，拓宽了壳聚糖的应用范围。这些衍生物的制备研究已成为壳聚糖应用开发的主要方向之一。 相似文献
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羧甲基壳聚糖中氨基葡萄糖含量测定方法的研究 总被引：8，自引：0，他引：8
以乙酰丙酮试剂结合分光光度法和以盐酸氨基葡萄糖为对照品，确定羧甲基壳聚糖的氨基葡萄糖含量测定方法。羧甲基壳聚糖在6mol／L HCl、120℃条件下水解2．5h，羧甲基壳聚糖水解样品溶液，效果较好；盐酸氨基葡萄糖对照品溶液和羧甲基壳聚糖水解样品溶液中的氨基葡萄糖与乙酰丙酮试剂进行定量反应，使溶液呈色，采用分光光度法进行定量分析，两者最大光吸收波长均为525nm，线性关系良好；该方法对氨基葡萄糖有较好的专属性、精密度和稳定性。可用于羧甲基壳聚糖的氨基葡萄糖定量分析。 相似文献
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硫酸化壳聚糖衍生物对实验性大鼠脂肪肝的治疗作用 总被引：2，自引：0，他引：2
研究硫酸化壳聚糖衍生物对实验性大鼠脂肪肝的治疗作用。采用定量灌胃酒脂乳剂的方法建立大鼠混合型脂肪肝模型。建模成功后的大鼠随机分为模型对照组和硫酸化壳聚糖治疗组,各组均饲以正常饲料,硫酸化壳聚糖治疗组采用腹腔注射给药,模型对照组以同等体积的生理盐水腹腔注射。治疗3周后,观察大鼠肝脏病理形态学变化,检测血清TC、HDL、LDL、AST、ALT和肝组织TG、AST、ALT、SOD含量。结果表明,硫酸化壳聚糖治疗组的肝组织形态较模型对照组有明显的好转,血清TC,HDL,LDL,AST,ALT和肝组织TG,AST,ALT含量显著降低,肝组织SOD含量增加;硫酸化壳聚糖治疗组血清TC,HDL,LDL,AST,ALT和肝组织TG,AST,ALT,SOD含量均恢复至正常对照组水平,硫酸化壳聚糖衍生物对大鼠脂肪肝有很好的治疗效果。 相似文献
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Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations. 相似文献
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《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献