无水磷脂DHPC的相变及水含量影响的DSC研究

利用差示扫描量热法,研究了无水及含水的1,2-双正十七烷酰基磷脂酞胆碱(DHPC)的相变特性.实验发现,无水DHPC初次受热时,首先发生玻璃态转变,接着像通常的晶体一样熔化.因此是玻璃性晶体.从熔体中结晶的DHPC是通常的晶体.从可以冻结水的总熔化培Q_f和水含量h的关系断定:在含水DHPC中,水可以存在于3种热力学上可区分的状态.第1种是不可冻结水,它是与磷脂头基直接结合的水,是一级水合水.每个头基最多可结合7个这样的水分子.第2种是二级水合水,其熔点接近于纯水但其比熔比焓dQ_f/dh比纯水的低.每个DHPC分子最多可保有约6个这样的水分子.当h再增大时,体系中有熔点及比熔化焓接近于纯水的体相水.实验发现,h增加,DHPC熔化峰向低温方向移动;当h>16.2%时,其凝胶-液晶相变温度T_tr及相交焓面△H_tr基本上不随h变化.T_tr、△H_tr及相变熵△S_(tr)的实验值和从偶数碳酰基磷脂酰胆碱同系物中得到的Huang(1981)方程组的计算值吻合.     

磷脂DHPC和短杆菌肽D相互作用的DSC研究

Changes of the behavior of the thermotropic phase transitions of the phospholipid DHPC by the action of miniprotein gramicidin D (G.D) have been studied by differential scanning calorimetry. The experimental results demonstrated that G.D could not remove the pretransition of DHPC, but the pretransition peak and the main transition peak of DHPC were incorporated into a broad peak. The pretransition temperature and the main transition temperature of DHPC decreased to different ex-tent. The sums of the pretransition and main transition enthalpies of DHPC showed a lineally decreasing relationship with increasing the mole fraction x_g of gramicidin D.     

过量水中脑磷脂假二元系相变的DSC研究

运用差示扫描量热法研究了过量水中脑磷脂 (DMPE和DHPE)假二元系的凝胶 液晶相变 ,给出该假二元系的相图 .实验表明 ,至少在DHPE的摩尔分数低于0 1时可能出现部分相分离现象 .理想溶液模型分析表明 ,既在凝胶相 ,又在液晶相 ,这两个脑磷脂都不理想混溶 ;正规溶液模型分析表明 ,凝胶相的非理想性参数更大     

稀土离子及其配合物对二棕榈酰磷脂酰乙醇胺相变性质的影响

用差示扫描量热研究了金属离子和稀土配合物对二棕榈酰磷脂酰乙醇胺(DPPE)脂双层由凝胶态向液晶态相转变的影响T~m的影响。发现加入金属离子提高了DPPE脂双层的相转变温度。其中, Na^+＜Ca^2^+＜Ln^3^+。Pr^3^+的影响较La^3^+强。在pH 7.4时, 柠檬酸镧对T~m影响很小, 相反在pH 2.0时, 则降低相变温度T~m。乳酸稀土在pH 2.0和pH 7.4时都显著提高T~m, 在中性条件下, 对T~m影响更大。同时, 乳酸稀土较相同浓度下的稀土离子影响大, 说明乳酸稀土中稀土离子和乳酸根配体存在协同作用。我们初步探讨了金属离子以及稀土配合物对DPPE脂双层相变温度影响的原因。     

大分子拥挤环境中脂肪酸影响磷脂囊泡相变的差示扫描量热研究

脂肪酸诱导的磷脂膜的热力学行为对于认识细胞内复杂的机制有着重要意义,而前人在研究脂肪酸与磷脂膜相互作用时大都在稀溶液中进行;拥挤环境下脂肪酸诱导磷脂膜的相变行为还未见报道。本文以二肉豆蔻酰磷脂酰胆碱(DMPC)构建囊泡模型,采用差示扫描量热法系统地研究了在不同浓度、不同分子量的聚乙二醇(PEG)拥挤环境中不同结构的脂肪酸对DMPC磷脂囊泡相变的影响。研究结果表明,在拥挤环境中,PEG对纯的磷脂囊泡相变的影响与大分子的分子量和浓度相关。对于脂肪酸/磷脂囊泡(FA/DMPC),PEG的存在对囊泡相变产生显著影响。在所考察的分子量和浓度范围内,PEG使FA/DMPC囊泡相变增加。短链饱和脂肪酸、不饱和脂肪酸原本使DPMC囊泡相变降低,但PEG缩小了降低幅度,甚至导致相变增加。进一步的研究表明,在大多数情况下,PEG对FA/DMPC的相变具有协作增强效应,且其影响均与大分子的分子量和浓度相关。另外,随着PEG浓度的升高,磷脂囊泡的协同单位数逐渐降低,表明拥挤环境会影响磷脂双分子层的均一性,使协同发生相变的分子数降低。本文的研究表明,大分子拥挤环境能够对扰动的磷脂双分子层起到一定的修复作用,这一现象在生物膜相关领域不可忽视。     

糖类对水合DHPE相变的影响

人们发现,许多据说是处在脱水生存（anhydrobiosis）状态下的干生物在无水情况下可以坚持存活数十年之久．在这些干生物体中经常包含大量的糖类和糖醇,而后两者似乎和这些生物在干燥状态存活有关[1]．此外,已经证明某些糖类能够保护磷脂膜[2]和细胞膜[3]不受冷冻和脱水造成的伤害．对耐干旱、耐霜冻生物的企求,对冷冻保存细胞、组织或器官时所用的冷冻保护剂（cryoprotectant）的求索,唤起了人们对糖类和磷脂膜相互作用研究的兴趣．在已经进行过的研究中,极大部分是使用磷脂酰胆碱（PC）或PC和磷脂酰丝氨酸的二元混合物作为形成双分…     

差示扫描量热法中相变潜热公式的推导

通过考虑热分析过程中存在于试样内的温度梯度,就相变前后试样的比热容发生变化、并且是温度的函数这一普遍情况,推导得到了普遍的用差示扫描量热法求相变潜热的公式     

电化学方法研究多粘菌素B与磷脂酰胆碱的相互作用

采用电化学方法研究了一种多肽类抗生素多粘菌素B(PMB)与模拟生物膜硫醇-磷脂酰胆碱杂化双层膜之间的相互作用。PMB可与磷脂酰胆碱发生强相互作用,破坏双层膜结构,从而使膜的通透性升高。PMB的浓度、酸度、与膜的作用时间及膜中胆固醇的存在均影响二者的作用程度。另外,膜的自修复实验表明,被PMB破坏的双层膜电极在一定程度上可以在KCl溶液中重新自组装,且自修复的程度和修复时间及与之相互作用的PMB的浓度有关。     

长链烷基胺氢卤酸盐的热致相变

差示扫描量热法（ＤＳＣ）结果表明，烷基胺氢卤酸盐化合物的相变温度与化合物烷基链链长之间存在明显的规律性，固－固结构相变的主相变峰温随烷基链链长的递增而升高，其逆相变过程表现出明显的热滞后现象；而熔融相变温度则随烷基链链长的递增而降低；实验结果还表明，试样的陈化放置过程以及结晶过程中所用的溶剂对化合物的热致相变历程都有明显的影响。     

DSC法研究液晶物质2-(4-烷氧苯基)6-取代苯并噻唑的相变热性质

众所周知,液晶类物质常因其特殊的理化性质而引起人们的兴趣,而拥有多种介晶相(mesomorphous phase)则为其主要特点之一.对于测定该类物质各种相变之间的热性质,差示扫描量热法(DSC)通常有其独特之处。2-(4-烷氧苯基)-6-取代苯并噻唑化合物为苏州大学化学系新研制的,样品经偏光显微镜、X射线衍射仪分析,发现其具有热致性液晶性能.我们用DSC法对这些化合物在升温及降温过程中的相变温度、相变焓进行了测定,并计算得到了相变熵。对于样品在冷却过程中的过冷现象作了测定和探讨.此外,还就样品处理对实验结果的影响作了初步的探索。     

DSC study of phase transition of anhydrous phospholipid DHPC and influence of water content

The phase transition behavior of 1,2-di-n-heptadecanoyl phosphatidylcholme (DHPC)with and without water has been studied by use of differential scanning calorimetry It was found by experiment that the glass transition occurred at first during the first heating of a sample of DHPC without water and then the sample underwent melting as an ordinary crystal.Therefore the sample of DHPC without water was a glassy crystal However,the DHPC sample crystallizing from melt was an ordinary crystal From the relationship between the total melting enthalpy Qf of freezable water and the water content h,it was concluded that the water contained in the DHPC samples might exist in three states recognizable thermodynamically.The water in the first state was an unfreezable water It was the water bound directly with the head groups of the phospholipid,i.e.the primary hydration water Every head group might bind seven such molecules of water.The water in the second state was the secondary hydration water,us melt ing point was     

Synthesis,Structural Study and Phase Transitions Characterization by Thermal Analysis and Vibrational Spectroscopy of an Ammonium Rubidium Arsenate Tellurate

The Rb_2.42(NH₄)_0.58(HAsO₄)(H₂AsO4)·Te(OH)₆ crystals(denoted by RbNAsTe) crystallize in the monoclinic system, space group P2₁/n with the following parameters:a=1.3059(5) nm, b=0.6755(3) nm, c=1.6675(6) nm, β=94.126(4)°, Z=4 and V=1.46733(10) nm³. Thermal analyses(DSC, DTA and TG) confirm the presence of the phase transition and the temperature of the decomposition. The vibrational spectroscopy study at room temperature show the presence and the independence of anionic groups, cationic groups, and give more importance to the hydrogen bonds. Raman spectra were recorded in the temperature range of 298-503 K. The temperature dependence of the Raman line shift, intensity reduction and the half width detects the phase transitions and confirms their nature. So, the phase transition at 453 K corresponds to the superprotonic-ionic conduction phase transition, and those at 483 and 491 K correspond to the decomposition of our material.     

DSC法研究液晶物质2-(4-烷氧苯基)6-取代苯并噻唑的相变热性质

The phase transitions of a new group of mesogens, 2-(4-alkoxyphenyl)-6-substituted benzothiazoles were thermodynamically studied by DSC, and their transition temperatures and enthalpy changes were measured, from which the transition entropy changes were calculated. The results obtained were discussed. In addition, the phe-nomenon of super-cooling of the compounds were quantitatively observed.     

2,2-二甲基-1,3-丙二醇在270～440K间的热容和相变

太阳能及废热等低温热能的储存是能源研究的重要领域之一。经调查和分析,我们认为,某些多元醇及其它物质也基本能满足低温储能的特性。此类物质已有一些零星的DSC研究结果,但系统的绝热量热学研究,特别是其混合物的热力学研究尚未见报道。作为多元醇及其混合物的绝热量热学研究的一部分,本文将报道2,2-二甲基-1,3-丙二醇在270～440K间的热力学性质和相变。     

Experimental Investigation on Binary Phase Diagram of the Thermotropic Phase Transitions Compounds (n‐CnH2n+1R3)2ZnCl4

The thermotropic phase transitions compounds (n‐C_nH_2n+1R₃)₂ZnCl₄ as well as a series of their binary mixtures were prepared by a solution reflux method from their ethanol solutions. The experimental subsolidus binary phase diagram of [n‐C₁₈H₃₇N(CH₃)₃]₂ZnCl₄‐[n‐(C₁₈H₃₇)₂N(CH₃)₂]₂ZnCl₄ is constructed over the entire composition range by differential scanning calorimetry(DSC) and X‐ray. Experi‐ mental results indicate one stable intermediate phase [n‐C₁₈H₃₇N(CH₃)₃] [n‐(C₁₈H₃₇)₂N(CH₃)₂]ZnCl₄ at W_C18C3Zn %=59.75 %, and two invariant three phase equilibria, which shows two eutectoid temperatures: Te₁ at 310±1 K for eutectoid point W_C18C3Zn %=36.24 %, Te₂ at 313±1 K for eutectoid point W_C18C3Zn %=80.17 %. These three noticeable solid‐solution ranges are α‐phase at the left, ?‐phase at the right, and ψ‐phase in the middle of the phase diagram. It is (n‐C_nH_2n+1R₃)₂ZnCl₄ systems as phase change materials that are characterized the phase transition temperatures T in the range of 310 to 340 K, the transition enthalpies ΔH in the range of 38.40 and 168.72 J/g between two polymorphic forms.     

TiO_2的相变和热力学性质(英文)

利用第一性原理平面波赝势密度泛函理论方法对TiO2从金红石结构到萤石结构的相变进行了理论研究,并且通过准谐德拜模型分别得到了金红石和萤石结构TiO2的热力学性质.计算结果与实验值以及其它理论计算的结果都符合得很好,通过吉布斯能的计算得到TiO2从金红石结构到萤石结构的相变压强为47.74GPa,并成功地获得了相对体积(V/V0)、德拜温度(Θ)和热容(CV)随压强(p)和温度(T)的变化关系.     

DSC study of phase transitions of cephalin pseudo-binary systems in excess water

The gel-liquid crystal phase transitions of the pseudo-binary systems of cephalins DMPE and DHPE in excess water were studied by differential scanning calorimetry. The phase diagram of the pseudo-binary systems has been given. The experiments showed that the partial phase separation in gel phase might occur at least at the mole fractions of DHPE below 0.1. The analysis by the model of ideal solution showed that both the cephalins were non-ideally miscible both in the gel phases and in the liquid crystal phases. The analysis by the model of regular solution showed that all the non-ideality parameters in the gel phases were larger than those in the liquid crystal phases at the same temperature. All the non-ideality parameters were not constant, but rather dependent on temperature.