Modeling interaction between gp120 HIV protein and CCR5 receptor

The study of the process of HIV entry into the host cell and the creation of biomimetic nanosystems that are able to selectively bind viral particles and proteins is a high priority research area for the development of novel diagnostic tools and treatment of HIV infection. Recently, we described multilayer nanoparticles (nanotraps) with heparin surface and cationic peptides comprising the N‐terminal tail (Nt) and the second extracellular loop (ECL2) of CCR5 receptor, which could bind with high affinity some inflammatory chemokines, in particular, Rantes. Because of the similarity of the binding determinants in CCR5 structure, both for chemokines and gp120 HIV protein, here we expand this approach to the study of the interactions of these biomimetic nanosystems and their components with the peptide representing the V3 loop of the activated form of gp120. According to surface plasmon resonance results, a conformational rearrangement is involved in the process of V3 and CCR5 fragments binding. As in the case of Rantes, ECL2 peptide showed much higher affinity to V3 peptide than Nt (K_D = 3.72 × 10^?8 and 1.10 × 10^?6 M, respectively). Heparin‐covered nanoparticles bearing CCR5 peptides effectively bound V3 as well. The presence of both heparin and the peptides in the structure of the nanotraps was shown to be crucial for the interaction with the V3 loop. Thus, short cationic peptides ECL2 and Nt proved to be excellent candidates for the design of CCR5 receptor mimetics.     

Superoxide anion scavenging activity of graft chitosan derivatives

Two kinds of graft chitosan derivatives (CMCTS-g-MAS and HPCTS-g-MAS) were prepared by the graft copolymerization of maleic acid sodium onto etherified chitosans-carboxymethyl chitosan (CMCTS) and hydroxypropyl chitosan (HPCTS), respectively. Superoxide anion scavenging activity of the derivatives was evaluated in a luminal-enhanced autoxidaton of pyrogallol by chemiluminescence techniques. Compared with chitosan, the graft chitosan derivatives have much improved scavenging ability against superoxide anion. They have similar 50% inhibition concentrations (IC₅₀s) as ascorbic acid and superoxide dismutase (SOD). Graft chitosan derivatives with hydroxypropyl groups have relatively higher superoxide anion scavenging ability owing to the incorporation of hydroxyl groups. The graft chitosan derivatives (HPCTS-g-MAS 1, 2, and 3) with different grafting percentages exhibit IC₅₀s values ranging from 243 to 308 μg/mL, which could be related to the contents of active hydroxyl and amino groups in the polymer chains.     

Photochemical Synthesis and Multiphoton Luminescence of Monodisperse Silver Nanocrystals

A rapid, photochemical solution-phase synthesis has been developed for the production of monodisperse, nanometer-sized silver particles. The stabilizer used in the synthesis can be used to control the average diameter of the particles over a range from 1 to 7 nm. The same reaction mixture can also be employed to deposit patterns of nanoparticles with a laser via multiphoton absorption. The particles exhibit strong multiphoton absorption-induced luminescence when irradiated with 800-nm light, allowing emission from single nanoparticles to be observed readily.     

二氧化氯在葡萄保鲜中的应用研究

用壳聚糖作涂膜剂,ClO2作保鲜剂,研究了葡萄的保鲜效果。结果表明,能有效的控制葡萄的腐烂率和鲜重损失,保持感官品质,延长存放期。     

壳聚糖对玉米生长的调节作用

应用壳聚糖衍生物羧甲基壳聚糖(NCMC)水溶液处理玉米种子,能够促进玉米种子的萌发,提高发芽势和发芽率.处理玉米果穗能够提高玉米未成熟籽粒的可溶性蛋白以及成熟种子的贮藏蛋白含量.以上结果表明,羧甲基壳聚糖对作物生长有调节功能.本文还初步研究了羧甲基壳聚糖对作物生长调控的机理.     

Constructing a collagen hydrogel for the delivery of stem cell-loaded chitosan microspheres

Multipotent stem cells have been shown to be extremely useful in the field of regenerative medicine. However, in order to use these cells effectively for tissue regeneration, a number of variables must be taken into account. These variables include: the total volume and surface area of the implantation site, the mechanical properties of the tissue and the tissue microenvironment, which includes the amount of vascularization and the components of the extracellular matrix. Therefore, the materials being used to deliver these cells must be biocompatible with a defined chemical composition while maintaining a mechanical strength that mimics the host tissue. These materials must also be permeable to oxygen and nutrients to provide a favorable microenvironment for cells to attach and proliferate. Chitosan, a cationic polysaccharide with excellent biocompatibility, can be easily chemically modified and has a high affinity to bind with in vivo macromolecules. Chitosan mimics the glycosaminoglycan portion of the extracellular matrix, enabling it to function as a substrate for cell adhesion, migration and proliferation. In this study we utilize chitosan in the form of microspheres to deliver adipose-derived stem cells (ASC) into a collagen based three-dimensional scaffold. An ideal cell-to-microsphere ratio was determined with respect to incubation time and cell density to achieve maximum number of cells that could be loaded. Once ASC are seeded onto the chitosan microspheres (CSM), they are embedded in a collagen scaffold and can be maintained in culture for extended periods. In summary, this study provides a method to precisely deliver stem cells within a three dimensional biomaterial scaffold.     

壳聚糖固定化AS1．398中性蛋白酶稳定性的研究

对以壳聚糖为载体,由戊二醛作交联剂。制备的固定化ＡＳ１．３９８中性蛋白酶的稳定性进行了研究。实验结果表明,固定化ＡＳ１．３９８中性蛋白酶对热、乙醇、尿素以及ｐＨ值的稳定性均有明显的提高。     

Electrochemical biosensor for the detection of cauliflower mosaic virus 35 S gene sequences using lead sulfide nanoparticles as oligonucleotide labels

Lead sulfide (PbS) nanoparticles were synthesized in aqueous solution and used as oligonucleotide labels for electrochemical detection of the 35 S promoter from cauliflower mosaic virus (CaMV) sequence. The PbS nanoparticles were modified with mercaptoacetic acid and could easily be linked with CaMV 35 S oligonucleotide probe. Target DNA sequences were covalently linked on a mercaptoacetic acid self-assembled gold electrode, and DNA hybridization of target DNA with probe DNA was completed on the electrode surface. PbS nanoparticles anchored on the hybrids were dissolved in the solution by oxidation of HNO₃ and detected using a sensitive differential pulse anodic stripping voltammetric method. The detection results can be used to monitor the hybridization reaction. The CaMV 35 S target sequence was satisfactorily detected with the detection limit as 4.38 × 10⁻¹² mol/L (3σ). The established method extends nanoparticle-labeled electrochemical DNA analysis to specific sequences from genetically modified organisms with higher sensitivity and selectivity.     

桦褶孔菌漆酶固定化及其对染料的降解

采用壳聚糖交联法和海藻酸钠-壳聚糖包埋交联法固定化桦褶孔菌产生的漆酶,探讨最佳固定化条件,固定化漆酶的温度,pH稳定性及操作稳定性,并以两种固定化酶分别对4种染料进行了降解.结果表明:(1)壳聚糖交联法固定化漆酶的最佳条件为:壳聚糖2.5%,戊二醛7%,交联时间2h,固定化时间5h,给酶量1g壳聚糖小球:1mL酶液(1U/mL),固定化效率56%;(2)海藻酸钠-壳聚糖包埋交联法固定化漆酶的最佳条件为:海藻酸钠浓度4%,壳聚糖浓度0.7%,氯化钙浓度5%,戊二醛浓度0.6%,给酶量4mL 4%海藻酸钠:1mL酶液(1U/mL),固定化效率高达86%;(3)固定化的漆酶相比游离漆酶有更好的温度和pH稳定性;(4)比较两种固定化漆酶,海藻酸钠-壳聚糖包埋交联法固定化酶的温度及酸度稳定性要优于壳聚糖固定化酶,但可重复操作性要弱于后者,两者重复使用8次后的剩余酶活比率分别为71%及64%;(5)两种固定化酶对所选的4种不同结构的合成染料均有较好的降解效果,其中壳聚糖固定化酶对茜素红的降解效果及重复使用性极佳,重复降解40mg/L的茜素红10次,降解率仍保持在100%.