Production of angiotensin-I-converting enzyme inhibitory peptides from β-lactoglobulin- and casein-derived peptides: an integrative approach

Angiotensin I-converting enzyme (ACE) inhibition is one of the mechanisms by which reduction in blood pressure is exerted. Whey proteins are a rich source of ACE inhibitory peptides and have shown a blood pressure reduction effect i.e. antihypertensive activity. The aim of this work was to develop a simplified process using a combination of adsorption and microfiltration steps for the production of hydrolysates from whey with high ACE inhibitory activity and potency; the latter was measured as the IC50, which is the peptide concentration required to reduce ACE activity by half. This process integrates the selective separation of β-lactoglobulin- and casein-derived peptides (CDP) from rennet whey and their hydrolysis, which results in partially pure, less complex hydrolysates with high bioactive potency. Hydrolysis was carried out with protease N "Amano" in a thermostatically controlled membrane reactor operated in a batch mode. By applying the integrative approach it was possible to produce from the same feedstock two different hydrolysates that exhibited high ACE inhibition. One hydrolysate was mainly composed of casein-derived peptides with IC50=285 μg/mL. In this hydrolysate we identified the well-known potent ACE-inhibitor and antihypertensive tripeptide Ile-Pro-Pro (IPP) and another novel octapeptide Gln-Asp-Lys-Thr-Glu-Ile-Pro-Thr (QDKTEIPT). The second hydrolysate was mainly composed of β-lactoglobulin derived peptides with IC50=28 μg/mL. This hydrolysate contained a tetrapeptide (Ile-Ile-Ala-Glu) IIAE as one of the two major peptides. A further advantage to this process is that enzyme activity was substantially increased as enzyme product inhibition was reduced.     

用D61大孔树脂从结晶母液中回收谷氨酸的研究

采用D61大孔氨型树脂,从等电点结晶母液中回收谷氨酸,上柱正交换,测出不同流率下的穿透曲线,得到交换区高度与交换速率的关系方程.同时采用3种试剂NH4Cl、(NH4)2SO4、NH3*H2O进行洗脱,其中NH3*H2O的洗脱效果较好,并测定了洗脱剂浓度和洗脱流率对洗脱效果的影响.     

湿地松无性系松脂组分分析及评价

为从湿地松种子园现有的速生材用无性系中选择产脂力强、松脂品质高的优良无性系,并高效利用湿地松良种资源。该研究以湿地松第一代种子园内36个无性系为材料,测定其树脂质量流速以及胸径生长量,进一步采用GC-MS分析其松脂组分,并基于上述指标利用相关性分析、聚类分析对参试的36个无性系进行综合评价。结果表明：(1)共鉴别出了21种松脂成分,包括8种单萜成分和13种二萜成分。(2)相关性分析显示,树脂质量流速(RMR)与单萜含量显著正相关,与枞酸型树脂酸呈弱的负相关,与海松酸型树脂酸无明显关联。(3)从松节油含量、树脂质量流速、枞酸型树脂酸、海松酸型树脂酸4个维度对参试无性系进行聚类分析,可将36个无性系分为三大类,并且各类型间差异显著,第1类的表现要远好于其他两类。(4)在产脂力高的基础上,6-44、4-11-1、1-38、3-64四个无性系单萜含量高,4-11-1、3-64、2-0420、3-468四个无性系海松酸型树脂酸含量高,而无性系2-173枞酸型树脂酸含量较高。该研究定性分析了湿地松的松脂组分,定量评估了36个无性系的产脂力与组分含量,为湿地松脂用无性系的选择奠定了基础。     

The effect of variation in light and nitrogen on growth and defence in young Sitka Spruce

1. Young plants of a northern (Alaska) and southern (Oregon) provenance of Sitka Spruce, Picea sitchensis , were subject to high and low light and high and low nitrogen treatments in a polyhouse experiment. The effect of treatments on growth, needle and resin duct size, water content and concentration of quantitative defences (resin and polyphenols), sugars and nitrogen in needles, stems and roots was determined.
2. Concentrations of resin, polyphenols and carbohydrates were higher in low nitrogen treatments as predicted by resource-availability models of defence and the changes were similar in all parts of the trees including roots and in tissues formed prior to experimental treatments. Variation in the relative concentration of resin and polyphenols between tissues may indicate a defensive trade-off. The size of needle resin ducts was positively correlated with tree growth but no evidence for 'structural' limitation of resin concentration in needles was found.
3. Changes in concentration of quantitative defences did not appear to be the result of a direct trade-off with growth but reflected treatment-induced variation in the root/shoot ratio. Production of quantitative secondary chemicals may therefore be part of an integrated response of the trees to environmental stress.
4. Bioassays with Elatobium abietinum, Gilpinia hercyniae and the fungus Phacidium coniferarum showed that changes in needle size, the nutritional and water content of tissues and the balance between nutrients and secondary chemicals influenced performance of one or more of the organisms. Changes in the concentration of carbon-based secondary chemicals alone were, therefore, of only limited value in predicting susceptibility of Spruce to insects and fungi.     

乳腺生物反应器表达产物层析分离过程中介质的污染机理及其再生策略

考察了磺酸基离子交换层析介质 (SP Sepharose FF) 在分离表达人乳铁蛋白的重组牛乳过程中的污染机理及其再生策略。通过层析原料及流分中各组分含量的检测分析,发现牛乳中的脂类通过堵塞效应或疏水相互作用残留在层析柱上,造成层析运行压力升高;部分酪蛋白通过静电相互作用占据介质的配基位点,导致介质的交换容量降低;乳糖与介质之间无直接相互作用。连续层析运行次数的增加以及层析-再生时间间隔的延长,均能导致残留组分和介质之间的相互作用逐渐增强,最终影响介质的再生效率。使用NaOH进行及时清洗,可以有效地清除柱上残留的脂类和蛋白,恢复离子交换介质的层析性能和微观形态。     

大孔吸附树脂纯化海红果黄酮工艺的研究

通过采用大孔吸附树脂对海红果黄酮粗提液的静态吸附和解吸试验,从10种大孔吸附树脂中筛选出海红果黄酮纯化的最优树脂,考察了该树脂对诲红果黄酮的静态、动态吸附与解吸性能并对吸附与洗脱的最佳条件进行了研究.结果表明:NKA-9树脂对海红果黄酮有很好的吸附和解吸性能,其最优的动态吸附工艺条件为:上样液pH值为4.0,浓度5.15 mg/mL,上样量为4 BV,流速控制在2 BV/h.最优的解吸工艺条件为:洗脱剂为80％乙醇溶液,洗脱液用量为3 BV,洗脱流速控制在1 BV/h.在此优化条件下,海红果黄酮的吸附率、解析率、收率、纯度的平均值分别达到为(79.39±0.13)％,(84.14±0.11)％,(68.20±0.15)％和(28.81 ±0.06)％ (n=5).     

Changes in fire regime break the legacy lock on successional trajectories in Alaskan boreal forest

Predicting plant community responses to changing environmental conditions is a key element of forecasting and mitigating the effects of global change. Disturbance can play an important role in these dynamics, by initiating cycles of secondary succession and generating opportunities for communities of long‐lived organisms to reorganize in alternative configurations. This study used landscape‐scale variations in environmental conditions, stand structure, and disturbance from an extreme fire year in Alaska to examine how these factors affected successional trajectories in boreal forests dominated by black spruce. Because fire intervals in interior Alaska are typically too short to allow relay succession, the initial cohorts of seedlings that recruit after fire largely determine future canopy composition. Consequently, in a dynamically stable landscape, postfire tree seedling composition should resemble that of the prefire forest stands, with little net change in tree composition after fire. Seedling recruitment data from 90 burned stands indicated that postfire establishment of black spruce was strongly linked to environmental conditions and was highest at sites that were moist and had high densities of prefire spruce. Although deciduous broadleaf trees were absent from most prefire stands, deciduous trees recruited from seed at many sites and were most abundant at sites where the fires burned severely, consuming much of the surface organic layer. Comparison of pre‐ and postfire tree composition in the burned stands indicated that the expected trajectory of black spruce self‐replacement was typical only at moist sites that burned with low fire severity. At severely burned sites, deciduous trees dominated the postfire tree seedling community, suggesting these sites will follow alternative, deciduous‐dominated trajectories of succession. Increases in the severity of boreal fires with climate warming may catalyze shifts to an increasingly deciduous‐dominated landscape, substantially altering landscape dynamics and ecosystem services in this part of the boreal forest.     

环氧树脂/氨基硅油胶粘剂的制备及其性能分析

用环氧树脂E-44和自制氨基硅油溶液聚合成改性环氧树脂,分析了环氧树脂与氨基硅油的配比、氨基硅油的氨值和特性粘度对改性环氧树脂的影响,并研究了固化剂4,4′-二氨基二苯甲烷(MDA)的固化条件对胶粘剂力学性能和粘接性能的影响。结果表明,氨基硅油用量为20%时所制备的改性环氧树脂的韧性最好;采用氨值为2.3 mmol·g~(-1),特性粘度为1.18 mL·g~(-1)的氨基硅油改性环氧树脂性能最好;制备胶粘剂时,以先在25℃固化3 h,后在120℃固化2 h为最佳工艺。     

乡村复合生态系统中村庄的社会经济生态位研究

为研究村庄社会经济子系统在乡村社会生态网络中的地位等级与未来发展潜力,提出社会经济生态位的概念,并以生态位的"态""势"理论为基础,利用主成分分析法、引力模型结构与社会网络分析方法对厦门岛外260个行政村的社会经济生态位进行计算。研究发现:(1)村庄社会经济生态位的"态"值分布具有不均衡性,厦门岛外村庄"态"值得分较高的村庄多聚集于厦门岛外南部与同安工业区。(2)村庄社会经济生态位的"势"值高低受地理空间与资源禀赋共同作用,厦门岛外"势"值得分较高的村庄集中在自身发展条件优越且地理位置处于区域核心位置的同安工业区与靠近厦门岛的集美大学城区。(3)相比自然子系统,乡村社会经济子系统更强调村庄之间的互动性,社会经济生态位得分中4个行政区村庄平均得分由高到低依次为集美区>同安区=翔安区>海沧区。研究为乡村复合生态系统的生态位研究提供了新的研究视角与方法,与传统生态位的计算方法相比更加强调村庄在实际发展中的互动性与带动作用,可以为村庄发展规划与居民福祉研究提供科学基础与理论依据。     

聚球藻7002嗜铁素的检测与分离

【目的】探究聚球藻7002嗜铁素的检测和分离方法,为深入研究海洋嗜铁素提供科学依据。【方法】在缺铁MediumA中培养聚球藻7002,利用双层平板法、混合平板法和传统铬天青S(CAS)平板法定性检测嗜铁素,用CAS蓝色液体检测液定量检测嗜铁素。采用大孔树脂XAD-2和固定化金属离子亲和层析(IMAC)对嗜铁素进行分离,IMAC采用降低pH和竞争性洗脱两种洗脱方式。【结果】混合平板定性检测法更快速、高效、便捷。缺铁培养的聚球藻7002发酵液中,嗜铁素的相对含量高达93.50%。大孔树脂分离,上样液pH调为2.0时,嗜铁素吸附充分,分离效果较好。试验发现,分离得到的聚球藻7002嗜铁素在254nm紫外下具有明显的荧光特性。【结论】试验得到了聚球藻7002嗜铁素定性检测和分离的有效方法。