Multispectroscopic studies on the interaction of 2-tert-butylhydroquinone (TBHQ), a food additive,with bovine serum albumin

The interaction of 2-tert-butylhydroquinone (TBHQ) and bovine serum albumin (BSA) was investigated by spectrophotometry, spectrofluorimetry, circular dichroism (CD) and FT-IR techniques. The experimental results indicated that the quenching mechanism of BSA by TBHQ was a static procedure. Various binding parameters were evaluated. The negative value of ΔH, positive value of ΔS and the negative value of ΔG indicated that hydrophobic and hydrogen bonding interactions play major roles in the binding of TBHQ and BSA. Based on Forster’s theory of non-radiation energy transfer, the binding distance, r, between the donor (BSA) and acceptor (TBHQ) was evaluated. The results of CD, UV–vis and FT-IR spectroscopy showed that the binding of TBHQ to BSA induced conformational changes in BSA.     

AG9/AB9与牛血清白蛋白相互作用的德拜休克尔极限理论分析及其焓熵补偿

本研究通过多光谱技术深入探讨盐浓度（离子强度）对酸性绿9（acid green 9,AG9）和酸性蓝9（acid blue 9,AB9）与牛血清白蛋白（bovine serum albumin,BSA）之间相互作用的影响。运用德拜休克尔极限理论定 量分析,计算得到真实的吉布斯自由能变化（ΔG0I →0）和BSA的阴离子受体腔内有效电荷（ZB）。配体AG9/AB9 所带电荷ZC的值为负,ZB的值为正,意味着相反电荷之间离子对的形成,即AG9/AB9的负电荷与BSA的净正电荷 结合腔（位点-Ⅰ）相结合,表明BSA的局部电荷主导BSA-AG9/AB9体系的相互作用,而不是它的整体或表面电 荷。随着盐浓度的增加,这两个体系的熵变逐渐由正值变为负值,且焓变逐渐增大,使ΔG0几乎不变而发生焓熵补 偿。最终其热力学参数由ΔH0＜0、ΔS0＞0（静电力）在高盐浓度下转变为ΔH0＜0、ΔS0＜0（非静电力）,表明 AG9/AB9与BSA相互作用时,它们的移动或局部运动由于主导力的转变而受阻。     

Mechanistic and conformational studies on the interaction of food dye amaranth with human serum albumin by multispectroscopic methods

The mechanism of interaction between food dye amaranth and human serum albumin (HSA) in physiological buffer (pH 7.4) was investigated by fluorescence, UV–vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopy. Results obtained from analysis of fluorescence spectra indicated that amaranth had a strong ability to quench the intrinsic fluorescence of HSA through a static quenching procedure. The negative value of enthalpy change and positive value of entropy change elucidated that the binding of amaranth to HSA was driven mainly by hydrophobic and hydrogen bonding interactions. The surface hydrophobicity of HSA increased after binding with amaranth. The binding distance between HSA and amaranth was estimated to be 3.03 nm and subdomain IIA (Sudlow site I) was the primary binding site for amaranth on HSA. The results of CD and FT-IR spectra showed that binding of amaranth to HSA induced conformational changes of HSA.     

Multispectroscopic studies on the interaction of maltol,a food additive,with bovine serum albumin

The interaction between maltol, a food additive, and bovine serum albumin (BSA) under simulated physiological conditions was investigated by fluorescence, UV–Vis absorption, circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy. The results suggested that the fluorescence quenching of BSA by maltol was a static procedure forming a maltol–BSA complex. The positive values of enthalpy change and entropy change indicated that hydrophobic interactions played a predominant role in the interaction of maltol with BSA. The competitive experiments of site markers revealed that the binding of maltol to BSA mainly took place in subdomain IIA (Sudlow site I). The binding distance between maltol and BSA was 3.01 nm based on the Förster theory of non-radioactive energy transfer. Moreover, the results of UV–Vis, synchronous fluorescence, CD and FT-IR spectra demonstrated that the microenvironment and the secondary structure of BSA were changed in the presence of maltol.     

分子对接和光谱法研究原儿茶醛和阿魏酸与牛血清白蛋白的互作机理

采用光谱法和分子对接技术分别研究原儿茶醛（protocatechuic aldehyde,PCA）和阿魏酸（ferulic acid,FA）与牛血清白蛋白（bovine serum albumin,BSA）的相互作用,同时比较PCA和FA分别与BSA的结合能力,从而揭示其相互作用机理,为其在食品领域的广泛应用提供实验依据。结果表明：PCA和FA主要靠氢键和范德华力与BSA形成稳定的复合物,由于ΔG小于0,所以此过程可自发进行;与FA相比,PCA与BSA之间的结合能力更强,PCA和FA与BSA各自均只有1 个位于Trp213残基附近IIA结合域和IIIA结合域之间疏水空腔中的结合位点,其最终导致BSA的内源荧光发生静态猝灭。此外,310 K时PCA与BSA相互作用的Ka值大于FA与BSA结合的Ka,其对应关系为9.005×105 L/mol＞2.553×105 L/mol;分子对接结果显示PCA比FA距离BSA的Trp213残基更近,其对应关系为0.512 nm＜0.518 nm,推测可能是因为PCA极性强于FA,所以PCA更容易与BSA结合。     

The influence of flavonoids on the binding of pantoprazole to bovine serum albumin by spectroscopic methods: With the viewpoint of food/drug interference

The interaction of pantoprazole to bovine serum albumin (BSA) has been investigated with and without four popular 5,7,3',4'-hydroxy-substituted flavonoids, quercetin, luteolin, taxifolin and (+)-catechin. The presence of flavonoids decreased binding constants of pantoprazole with BSA from 39.7% to 93.8%, which depended on flavonoid structures. Analysis of infrared spectroscopy (IR) and circular dichroism (CD) showed the binding of pantoprazole to BSA caused apparent change in secondary structure of BSA. The calculated values of spatial-distance indicated the existence of quercetin, luteolin and taxifolin may compete with pantoprazole binding to BSA, while the existence of (+)-catechin possibly formed ternary pantoprazole-BSA-(+)-catechin complex. However, all the fluorescence quenching was initiated by static quenching procedure irrespective of the absence or presence of flavonoids, while van der Waals force and hydrogen bonds played major roles for pantoprazole-BSA association. All above results may have relevant consequence in rationalising the interferences of common food to gastric ulcer treatments.     

亚甲基蓝及其代谢产物与牛血清白蛋白相互作用的研究

采用多种光谱法研究了亚甲基蓝(MB)及其代谢产物天青B(AZB)与牛血清白蛋白(BSA)之间的共同作用机制。实验结果表明,MB和AZB对BSA的荧光猝灭均为静态猝灭。298K时MB和AZB与BSA的结合常数分别为1.71×10⁵ L/mol和8.83×10⁴ L/mol。由熵和焓推断,MB和AZB与BSA的作用力类型均主要为静电作用。位点竞争实验结果表明MB和AZB均结合在BSA的SiteⅠ。紫外-可见吸收光谱法实验结果表明,MB和AZB诱导BSA的构象改变。三者共存时,AZB会与MB竞争结合BSA,减小MB与BSA作用的猝灭常数和结合常数,改变MB与BSA的作用力类型。     

分子对接和荧光光谱法研究麦角甾醇与牛血清白蛋白的相互作用

用分子荧光光谱实验法和分子对接理论研究麦角甾醇与牛血清白蛋白（bovine serum albumin,BSA）的相互作用。荧光光谱实验结果表明：麦角甾醇能猝灭BSA的内源性荧光,其猝灭类型为静态猝灭;通过考察猝灭过程中热力学函数的变化初步推断麦角甾醇与BSA的结合是自发的熵增过程,驱动力主要为疏水相互作用。运用分子对接技术研究了麦角甾醇与BSA的相互作用,结果表明：麦角甾醇与BSA相结合,主要的作用力类型为疏水相互作用;并获得了麦角甾醇在BSA中的作用位点,麦角甾醇处在一个疏水性的结合口袋中,结合稳定性强。荧光光谱的实验结果与分子对接的理论结果总体上一致,说明结合过程是一个自发的过程,BSA可以携带和运输麦角甾醇,同时从分子对接中获得了麦角甾醇在BSA中详细的结合位点和结合模式。     

荧光光谱法研究链格孢霉毒素TeA与血清白蛋白的互作机理

链格孢霉毒素是由链格孢霉菌属(Alternaria species)产生的次级代谢产物,在水果、蔬菜以及粮食作物中污染率极高,可通过多种途径进入人类食物链,引发食品安全问题.为研究链格孢霉毒素细交链格孢菌酮酸(Tenuazonic Acid,TeA)在动物体内的吸收、分布、转运及代谢,本文采用稳态荧光光谱、同步荧光光谱...     

荧光光谱法探究pH值对叶黄素与牛血清白蛋白相互作用的影响

采用荧光光谱法研究不同pH值（3.0、5.2、7.4）条件下叶黄素与牛血清白蛋白（bovine serum albumin，BSA）的相互作用，利用数学模型计算得到二者的猝灭常数和热力学参数等，分析叶黄素与BSA的荧光猝灭现象及蛋白构象的变化，最后通过位点竞争实验和分子模拟技术确定了二者的结合位点。荧光光谱表明，不同pH值条件下叶黄素对BSA均产生荧光猝灭效应，在298 K时，pH 7.4的猝灭常数最大，结合常数较大；热力学参数和分子对接结果表明，叶黄素与BSA间的作用力主要是疏水相互作用；同步荧光光谱表明BSA的构象在叶黄素与pH值的共同作用下发生改变；位点竞争性实验和分子对接实验表明，pH 7.4和pH 5.2时，二者的结合位点在亚结构域IIA和IIIA之间，但更接近于Sudlow’s site II；pH 3.0时，结合位点不在亚结构域IIA及IIIA附近。结果表明，pH值对叶黄素和BSA的相互作用有影响，这为蛋白质与生物活性成分的相互作用提供一定的理论依据。     

Water Sorption of Coffee Solubles by Frontal Inverse Gas Chromatography: Thermodynamic Considerations

Information on the sorption mechanism was obtained by investigating the thermodynamic relationships of moisture in freeze-dried coffee by frontal inverse gas chromatography. The thermodynamic parameters ΔG_S, ΔH_S and ΔS_S were calculated. The negative ΔG_S values obtained for water sorption of coffee under all conditions indicated the existence of strong hydrophilic sites in the coffee matrix. Also, the enthalpic and entropic changes showed a distinctive moisture content dependence which reflected a shift from surface sorption at restricted heterogeneous active sites to sorption at more homogeneous binding sites in the bulk phase and structural changes induced by swelling from multimolecular water that occupied the hydrophilic sites.     

Spectroscopic studies on the interaction of sodium benzoate,a food preservative,with calf thymus DNA

The interaction between sodium benzoate (SB) and calf thymus DNA in simulated physiological buffer (pH 7.4) using acridine orange (AO) dye as a fluorescence probe, was investigated by UV–Vis absorption, fluorescence and circular dichroism (CD) spectroscopy along with DNA melting studies and viscosity measurements. An expanded UV–Vis spectral data matrix was resolved by multivariate curve resolution-alternating least squares (MCR−ALS) approach. The equilibrium concentration profiles and the pure spectra for SB, DNA and DNA–SB complex from the high overlapping composite response were simultaneously obtained. The results indicated that SB could bind to DNA, and hydrophobic interactions and hydrogen bonds played a vital role in the binding process. Moreover, SB was able to quench the fluorescence of DNA−AO complex through a static procedure. The quenching observed was indicative of an intercalative mode of interaction between SB and DNA, which was supported by melting studies, viscosity measurements and CD analysis.     

花青素对牛血清白蛋白的光谱特性及构象的影响

为研究模拟生理条件下花青素（ACN）对牛血清白蛋白（BSA）的光谱特性及对BSA功能构象的影响,本文采用荧光光谱法判定ACN对BSA的猝灭方式、结合位点数、结合位点、结合作用力类型以及是否发生非辐射能量转移;利用紫外-可见吸收光谱法、圆二色谱法、傅利叶红外吸收光谱法进一步表征了BSA构象变化。结果表明,在ACN的作用下,BSA内源荧光被有规律的猝灭,猝灭机制主要为形成ACN-BSA复合物的静态猝灭和非辐射能量转移。猝灭过程是自发进行的,结合位点数约为1,结合位点位于BSA亚结构域的site I,并使得BSA二级结构中α-螺旋含量减少了3.1%。ACN对BSA有较强的结合能力,并能使BSA构象发生变化。     

苦丁冬青苦丁茶中咖啡酰奎尼酸类物质与牛血清白蛋白的相互作用

从苦丁冬青苦丁茶中分离纯化得到了4 种咖啡酰奎尼酸（caffeoylquinic acids,CQA）：5-CQA、3,4-diCQA、3,5-diCQA和4,5-diCQA,并在模拟人体生理条件（pH 7.4,310 K）下,利用荧光光谱法分析4 种CQA与牛血清白蛋白（bovine serum albumin,BSA）的相互作用,使用修正后的Stern-Volmer方程与van’t Hoff方程探讨CQA-BSA之间的结合常数、结合位点数及热力学参数。结果表明：4 种CQA均能与BSA结合,从而导致BSA分子内部荧光发生猝灭,结合能力的大小顺序为3,4-diCQA＞3,5-diCQA＞4,5-diCQA＞5-CQA,说明咖啡酰基的增多提高了结合能力。热力学参数ΔH＞0、ΔS＞0和ΔG＜0,表明CQA与BSA主要靠疏水作用力结合,反应自发进行。此外,CQA的结合引起BSA 3D荧光光谱和同步荧光光谱的变化,表明两者之间的结合主要是通过与BSA中色氨酸和酪氨酸的作用而实现的。     

基于光谱法研究异细交链孢菌酮酸半抗原-抗体的相互作用

本文采用紫外可见光谱(UV-Vis)、荧光光谱和圆二色谱(CD)技术研究了异细交链孢菌酮酸单克隆抗体(Mc Ab)与其半抗原(Ite AH)之间的相互作用并用ELISA方法对荧光结果进行了验证。结果表明,ITe AH对Mc Ab有荧光猝灭作用,淬灭机理主要为静态猝灭且遵循非辐射能量转移理论。在298、310、318 K 3个温度下,ITe AH与Mc Ab的结合常数分别为1.9×106、1.6×106、1.4×106 L/mo L,结合位点数n≈1,结合距离r为3.35 nm,经ELISA测得的结合常数与荧光分析的结果较一致。由结合作用过程的热力学参数可知,两者之间以静电引力为主要作用力,不同p H下,由ELISA结果可推测其影响了ITe AH与抗体结合。同步荧光光谱显示ITe AH的加入并未使抗体的酪氨酸和色氨酸残基附近的微环境发生明显改变,两者的结合位点更倾向于酪氨酸残基,圆二色谱分析发现ITe AH与Mc Ab相互作用后,抗体的二级结构发生明显变化。     

Structure-affinity relationship of bovine serum albumin with dietary flavonoids with different C-ring substituents in the presence of Fe ion

The relationship of four dietary flavonoids, quercein (QU), luteolin (LU), taxifolin (TA) and (+)-catechin (CA), with different C-ring substituents binding with bovine serum albumin (BSA) have been investigated in the absence and presence of Fe³⁺ by means of spectroscopic methods. The quenching constant (K_SV), binding constant (K_a), binding site number (n) and spatial-distance (r) of flavonoids with BSA were calculated. The results indicated that hydroxyl group at 3-position and C2–C3 double bond affected the binding affinities between flavonoids and BSA. The values of the binding affinities were in the order: QU > CA > TA > LU. The presence of Fe³⁺ affected the interactions between flavonoids and BSA significantly, and the influence was distinct for the flavonoids with different C-ring structures. The binding affinities of QU, LU and CA for BSA were increased about 0.85%, 41.3% and 56.8% in the presence of Fe³⁺, probably because of the formation of QU–Fe³⁺–BSA complex, Fe³⁺–LU complex and the conformational change of BSA induced by Fe³⁺, respectively. The binding affinities of TA for BSA were decreased about 20.7%, mainly because of the existence of competitive binding between TA and Fe³⁺ with BSA. However, the quenching mechanism for QU, LU, TA and CA to BSA were based on static quenching combined with non-radiative energy transfer irrespective of the absence or presence of Fe³⁺ ion.     

苦丁皂苷L、苦丁皂苷N与牛血清白蛋白的相互作用研究

为研究不同温度下苦丁皂苷L(kudinoside L)、苦丁皂苷N(kudinoside N)与牛血清白蛋白(BSA)间结合和转运的机制及BSA二级结构变化情况。采用荧光光谱法研究kudinoside L、kudinoside N与BSA间荧光猝灭机制;采用圆二色谱法研究BSA二级结构的变化情况。结果表明kudinoside L、kudinoside N均能有效猝灭BSA内源荧光,猝灭类型为动态猝灭,分子间作用力主要为疏水作用,两个化合物与BSA各形成1个结合位点。此外,kudinoside L与BSA结合后,BSA中的α-螺旋和β-折叠含量增加;kudinoside N与BSA结合后,BSA中α-螺旋和无规卷曲含量减少,表明上述两种皂苷与BSA结合后,BSA内部结构环境均发生了改变。     

二价铜离子对分散红3B染色性能的影响

探讨了二价铜离子对分散红3B染色性能的影响,研究了二价铜离子存在时助剂TA(三聚氰胺)和CD(β-环糊精)对分散红3B染色性能的影响.结果表明:铜离子对分散红3B染料吸光度和染色K/S值的影响很大,K/S值的下降与铜离子浓度有关,容易引起色光向短波长偏移且得色变浅.而助剂TA和CD会使分散红3B的吸光度和K/S值下降,但是有利于染色织物色相的稳定性.     

壳聚糖/纤维素硫酸酯复合小球的制备及其对BSA吸附性能的研究

以离子液[Emim]Ac为溶剂,采用挤球法制备壳聚糖/纤维素硫酸酯(CHT-CS)复合小球,探索制备条件,并用FT-IR、SEM和XRD对其进行表征。将复合小球用于吸附牛血清蛋白(BSA),考察影响CHT-CS吸附BSA的因素。结果表明:制备复合小球的最佳条件是纤维素酸酯的取代度为0.58,复合原料液的浓度为5%,壳聚糖:纤维素硫酸酯为1:1;纤维素硫酸酯和壳聚糖在制备过程中发生了复杂的相互作用,形成了结构稳定,表面和内部均存在大量沟壑和孔洞的小球;所制备的复合小球对BSA的最大平衡吸附量达到157 mg/g,高于其他壳聚糖复合材料;当BSA初始浓度1 mg/m L、溶液p H为5左右,小球对BSA的吸附量最大;一定范围内增加小球投加量在可增大BSA吸附量。本研究结果为分离纯化BSA和CHT-CS复合小球固定化酶等方面的应用提供了参考。     

黄芩甙在蚕丝上的染色热力学研究

为了探讨天然染料黄芩在蚕丝纤维上的染色机制,提高其对上染过程控制、染色效果预测及染色工艺优化的指导价值,对蚕丝纤维先用铝离子预媒染后用黄芩提取物黄芩甙进行染色平衡实验。运用3种理论吸附模型即Langmuir、Freundlich和Nernst对30、45、60℃下的实验数据进行模拟,计算黄芩甙在蚕丝纤维上的热力学参数。结果表明,黄芩甙在蚕丝上的吸附最符合Langmuir吸附模型,并用拟合系数和正规偏差验证了吸附模型,该过程是吸热过程,染色热为2.303 4 kJ/mol,染色熵为6 J/mol,染色亲和力和饱和吸附量随温度的升高而增加。