Solid-state NMR of the retinal protonated Schiff base in microbial rhodopsins

Rhodopsin is a seven-helical transmembrane protein with a retinal chromophore covalently bound to a conserved lysine in helix G via a retinal protonated Schiff base(RPSB).Microbial rhodopsins absorb light through chromophore and play a fundamental role in optogenetics.Numerous microbial rhodopsins have been discovered,contributing to diverse functions and colors.Solid-state NMR spectroscopy has been instrumental in elucidating the conformation of chromophores and the three-dimensional structure of microbial rhodopsins.This review focuses on the 15N chemical shift values of RPSB and summarizes recent progress in the field.We displayed the correlation between the 15N isotropic chemical shift values of RPSB and the maximum absorption wavelength of rhodopsin using solid-state NMR spectroscopy.

Synthesis and Characterization of Novel Schiff Base for Enhanced Dye-Sensitized Solar Cell Photo-Response Mechanism

The efficient photo-response mechanism is one of the key factors in the commercialization of dye-sensitized solar cells in a bid to satisfy renewable energy demands. Progress in green technology has put solar energy on the front burner as a provider of clean and affordable energy for a sustainable society. We report the synthesis of a novel Schiff base with optical transparency in the visible and near IR region of the solar spectrum that can find application in the DSSCs photo-response mechanism. The synthesized crystal exhibited features that could handle some of the shortcomings of dye-sensitized solar cells which include wide band solar spectrum absorption and capability for swift charge transfer within the photoelectrodes. The synthesized Schiff base was characterized using x-ray diffractometer, UV/Visible spectrometer, Frontier transmission infrared spectrometer and conductometer. XRD data revealed the grown crystal to have an average crystallite size of 2.08 nm with average microstrain value of about 269.43. The FT-IR recorded transmission wave ѵ (CO) at 1207.7 cm−1 while dominant wave occurred at ѵ1654.9 and ѵ1592.3 cm−1 relating to ѵ (CN) stretching and ѵ (NH) bending respectively were observed. The IR spectrum revealed the bonding species and a probable molecular structure of 2,6-bis(benzyloxy)pyridine. The UV/Visible spectra convoluted to maximum peak within the near IR region suggesting that 2,6-bis(benzyloxy)pyridine can absorb both the visible and near IR region while its electrical conductivity was determined to be 4.58 µS/cm. The obtained result of the present study revealed promising characteristics of a photosensitizer that can find application in the photo-response mechanism of DSSCs.

In vitro degradation resistance of glucose and L-cysteine-bioinspired Schiff-base anodic Ca−P coating on AZ31 magnesium alloy

A Schiff base(a compound containing a C=N bond)induced anodic Ca−P coating was prepared on AZ31 Mg alloy in a mixed solution of CaCl_(2) and KH_(2)PO_(4) at 60℃ in the presence of glucose and L-cysteine.The microstructure and chemical composition of the coatings were characterized using FE-SEM,FT-IR,XRD,and XPS.The in vitro degradation resistance of the coated samples was evaluated via potentiodynamic polarization(PDP),electrochemical impedance spectroscopy(EIS),and hydrogen evolution test.The experimental results show that the Ca−PSchiff base coating is composed of CaHPO_(4)(DCPA)and hydroxyapatite(HA),whereas HA is not present in the Ca−P coating.The Ca−P_(Schiff base) coating thickness is about 2 times that of Ca−P coating(Ca−P coating:(9.13±4.20)μm and Ca−P_(Schiff base):(18.13±5.78)μm).The corrosion current density of the Ca−P_(Schiff base) coating is two orders of magnitude lower than that of the Ca−P coating.The formation mechanism of the Ca−P_(Schiff base) is proposed.

固体推进剂用新型Schiff碱类高效键合剂的合成及性能表征

为提高丁羟四组元推进剂和CL-20/GAP推进剂的力学性能,解决新的推进剂填料基体界面“脱湿”问题,设计合成了新型Schiff碱键合剂;采用傅里叶红外光谱仪、扫描电子显微镜及万能材料拉伸机等对键合剂的键合效果和推进剂的力学性能进行了表征。结果表明,合成的新型Schiff碱键合剂包含键合剂必备官能团且在AP表面存在明显键合,新型Schiff碱键合剂有望取代有毒MAPO,可明显提高丁羟四组元推进剂的力学性能,使丁羟四组元推进剂常温拉伸强度达到0.7 MPa,常温延伸率大于55%,高温延伸率大于50%,低温延伸率大于60%,并可以明显改善丁羟四组元推进剂的工艺性能;在CL-20/GAP推进剂中,新型Schiff碱键合剂可同时提高推进剂的拉伸强度和延伸率。

Synthesis, Characterization and Biological Activity Evaluation of Schiff Bases Derived from 1,8-Diaminonaphtalène

The compounds have been synthesized and characterized by routine MS, IR and NMR spectrometry methods. The compounds are all active on bacterial strains with the exception of Salmonella typhimirium, with a MIC value of 7.5 mg/mL. They show a percentage of anti-radical activity of 75.476 ± 5.070 for the compound DAN-S and of 68.142 ± 6.539 for the compound DAN-OV. The compounds are sensitive to the two champions used. DAN-S compound is then the most active.

Coordination and Photoisomerization of Azobenzene-Amino Acid Schiff Base Copper(II) Complexes to Lysozyme

In this study, we exhibited an amino acid (arginine and threonine) derivative Schiff base copper(II) complexes incorporating an azobenzene moiety as a photoresponsive site and conjugated it to egg white lysozyme, a well-known protein, to change ligand conformation under binding to lysozyme. Among several spectroscopic investigations, ESR clearly showed that the nitrogen atom of the amino acid residue of lysozyme was bound to the paramagnetic copper(II) ion of the complex, and UV light irradiation confirmed photoisomerization of the azobenzene moiety of the ligand to cis-form. The binding mode was considered by means of spectroscopic as well as computational methods, whereas complete crystallographic verification was still a preliminary stage.

Synthesis and Characterisation of Cr(III) and Co(II) Schiff Base Complexes

Co(II) and Cr(III) metal complexes of Schiff bases were synthesized from the condensation reaction between 4-(dimethylamino)benzaldehyde and 4-amino-3-hydroxy-naphthalene-1-sulfonic acid. Their structures were investigated by elemental analysis, molar conductance measurements, infrared spectroscopy, electronic spectroscopy, and 1HNMR spectroscopy. The elemental analysis data suggested a 1:1 [M:L] ratio for the complexes. The molar conductance measurements of the complexes indicate their electrolytic nature in DMSO as a solvent. The absorption bands in the electronic spectra verified an octahedral environment around the metal ions in the complexes.

Flexible,thermal processable,self-healing,and fully bio-based starch plastics by constructing dynamic imine network

The serious environmental threat caused by petroleum-based plastics has spurred more researches in developing substitutes from renewable sources.Starch is desirable for fabricating bioplastic due to its abundance and renewable nature.However,limitations such as brittleness,hydrophilicity,and thermal properties restrict its widespread application.To overcome these issues,covalent adaptable network was constructed to fabricate a fully bio-based starch plastic with multiple advantages via Schiff base reactions.This strategy endowed starch plastic with excellent thermal processability,as evidenced by a low glass transition temperature(T_(g)=20.15℃).Through introducing Priamine with long carbon chains,the starch plastic demonstrated superior flexibility(elongation at break=45.2%)and waterproof capability(water contact angle=109.2°).Besides,it possessed a good thermal stability and self-adaptability,as well as solvent resistance and chemical degradability.This work provides a promising method to fabricate fully bio-based plastics as alternative to petroleum-based plastics.

1-苯基-3-(1-环己胺)-丙烯Schiff碱缓蚀剂在盐酸溶液中对J55钢的缓蚀效果

为改善酸化压裂施工造成的腐蚀问题,以肉桂醛和环己胺为原料合成了Schiff碱酸化缓蚀剂1-苯基-3-(1-环己胺)-丙烯(PCP),通过红外光谱和气相色谱-质谱联用对其结构进行表征,并采用失重法、电化学(极化曲线、阻抗谱、噪声)及分子动力学模拟等方法评价了PCP的缓蚀效果。结果表明,合成产物即为目标产物PCP。在15%HCl、90℃的条件下,随着PCP浓度增加,J55钢的失重腐蚀速率及腐蚀电流密度显著减小,缓释率逐渐增大。不同PCP加量下的缓释率均可达到99%以上,缓蚀效果较好。在PCP加量达到0.15%时,腐蚀速率及缓释率随着缓蚀剂浓度的增加整体变化不大,即缓蚀剂在J55钢表面的吸附浓度已达到临界胶束浓度,吸附量不再发生变化。PCP同时抑制了阴极析氢和阳极溶解反应,为混合型缓蚀剂。随着PCP浓度的增加,容抗弧半径、极化电阻及噪声电阻由小到大的排序均为:空白﹤0.05%﹤0.10%﹤0.15%﹤0.20%;低频的白噪声水平在电流PSD图中随着PCP浓度的增加而减小,即J55钢的腐蚀速率不断减小,与失重法及极化曲线反应的规律一致。当PCP分子与金属发生吸附并达到平衡时,整个缓蚀剂分子处于同一平面,平行吸附在J55钢表面,达到完全覆盖,从而有效减缓了腐蚀介质的侵入。

对羟基苯甲醛Schiff碱的合成、表征及生物活性

Schiff是优良配体,并具有抑菌、抗氧化和抗肿瘤等生物活性。以对羟基苯甲醛为原料,分别与4-甲基、5-甲基-2-氨基吡啶反应,合成了2个对羟基苯甲醛Schiff碱,即对羟基苯甲醛缩4-甲基-2-氨基吡啶(1)和对羟基苯甲醛缩5-甲基-2-氨基吡啶(2)。采用熔点、红外光谱、紫外可见光谱、核磁共振氢谱和碳谱以及高分辨质谱等对产物结构进行了全面表征。利用微量肉汤稀释法研究其抑菌活性,结果标明:化合物1和化合物2对大肠杆菌、金黄色葡萄球菌和枯草芽孢杆菌的最小抑菌浓度(MIC)为0.500 mg/mL,对溶藻性弧菌、副溶血性弧菌的MIC为0.250 mg/mL。采用DPPH·法研究了化合物1的抗氧化活性,发现其对DPPH·自由基清除率为68.1%。

含香豆素骨架水杨醛Schiff base荧光材料的制备及光谱性能研究

以间苯二酚和乙酰乙酸乙酯为原料,草酸做催化剂,在无溶剂的条件下,经Pechmann反应催化合成了7-羟基-4-甲基香豆素,再经硝化、还原得到3-氨基7-羟基-4-甲基香豆素。利用3-氨基7-羟基-4-甲基香豆素与水杨醛缩合反应,制备了新型的含香豆素骨架水杨醛Schiff base衍生物,其结构由IR、1HNMR和元素分析确证。通过研究化合物紫外吸收光谱及荧光光谱发现该化合物具有优异光学活性。

以Schiff base为配体的Cu(Ⅱ)-金属凝胶的制备和表征

以间苯二甲醛分别与异烟肼、烟酸酰肼和2-吡啶甲酰肼反应,合成了3种含吡啶环的Schiff base配体间苯二甲醛双缩4-吡啶甲酰腙(S1)、间苯二甲醛双缩3-吡啶甲酰腙(S2)和间苯二甲醛双缩2-吡啶甲酰腙(S3);测试了这3个化合物与醋酸铜通过配位作用在不同溶剂中形成金属凝胶的能力,结果发现,配体S1与醋酸铜在DMF/H_2O和DMSO/H_2O的混合溶剂中、配体S3与醋酸铜在DMF/H_2O的混合溶剂中均可以形成金属凝胶。胶凝测试结果表明,吡啶环上N原子位置的不同,对化合物形成金属凝胶的能力有极大影响。利用扫描电子显微镜(SEM)观察了金属凝胶的微观形貌,结果表明,配体分子的结构对金属凝胶的微观形貌也有较大影响;红外光谱和紫外可见光谱的研究证明了配位作用在金属凝胶形成过程中的推动作用;X射线衍射分析(XRD)研究表明,配体S1与醋酸铜在两种混合溶剂中形成的金属凝胶均表现出了四方堆积结构。

5-硝基水杨醛氨基酸Schiff-bases铜配合物与DNA相互作用的研究

用电子光谱、荧光淬灭光谱和循环伏安的方法,研究了(苯丙氨酸缩5-硝基水杨醛)铜(1)和(组氨酸缩5-硝基水杨醛)铜(2)与 DNA 的作用.结果表明,配合物均以插入模式与 DNA 作用;配合物与 DNA 作用强弱为:配合物(2)>配合物(1).

脱氢枞胺水杨醛类席夫碱(Schiff Bases)对铜离子萃取性能的研究

合成5种脱氢枞胺水杨醛类Schiff碱,对其萃取铜离子的影响因素进行研究,并与萃取剂N902对电镀废水中铜离子的萃取性能进行了比较。结果表明:萃取温度和萃取时间对铜离子萃取率的影响不明显,萃取温度在20～30℃、萃取时间为2 h就能达到萃取平衡;大部分Schiff碱在低pH范围内对铜离子的萃取效果不理想,在高pH范围内有较好的萃取性能。DHAA 2,3,4-三羟基苯甲醛的萃取效果与N902相当。

基于Schiff-base结构化合物载体的汞离子选择性电极的制备与表征

高产率合成了一种新的Schiff-base结构化合物，并将其表征为高选择性聚合物膜汞离子选择性电极载体。考察了不同增塑剂及离子交换剂对膜电极响应性能的影响，在最佳膜组分条件下测得该电极对汞离子的线性响应范围为1．0×10^-6-3．0×10^-4mol／L，响应斜率为（29．3±0．3）mV／dec，检出限为2．6×10^-7mol/L；该电极响应速率快（小于12s），可在较宽的pH范围内（pH2．8～5．6）使用，且其它常见碱金属、碱土金属以及过渡金属离子对该测试电极的干扰小；可准确检测自来水中汞离子的浓度。

聚甲亚胺(Schiff base)的研究进展

综述了聚甲亚胺的研究进展,结合本课题组的工作,评述了聚合物合成、结构及各种性能、存在的问题,指出了研究前景与发展方向.

手性Schiff Base-Ti(OR)_4配合物催化醛的不对称硅腈化反应

设计合成了新型手性Ｓａｌｅｎ－Ｔｉ（ＯＲ）４配合物催化剂，用其催化一系列醛的不对称硅腈化反应，得到了ｅ．ｅ．值为２２．４％～８７．１％的氰醇．催化剂中抗衡离子的Ｌｅｗｉｓ碱强烈地影响催化活性，但对反应的对映选择性影响很小，并探讨了其不对称催化反应机理．

Schiff bases及配合物的研究进展

希夫碱配体及与后过渡金属元素所形成的配合物,以其多样的结构和广泛的用途愈来愈受到人们的重视。文章综述了Schiff base配体及配合物的发展状况以及在生物化学、催化化学、分析化学、材料化学等方面的研究与应用,并指出了它的美好前景。

手性三齿Schiff-base配体的合成及其催化的不对称Henry反应研究

以L-酪氨酸甲酯盐酸盐为原料,通过格氏反应合成了一种手性β-氨基醇;以水杨醛为原料,通过溴代反应合成了3,5-二溴水杨醛和5-溴水杨醛;将手性β-氨基醇和溴代水杨醛在乙醇中缩合,制备了两种手性三齿Schiff-base配体.产物的结构经IR,1 H NMR,13C NMR和MS表征确定.将配体应用于催化不对称Henry反应中,考察其在不同反应条件下的催化性能,在最优化的反应条件下,不同底物均获得了较好的催化效果,产率最高达95%,ee值最高达90%.

Ru(Schiff-base)/Y复合材料对苯加氢反应的催化性能研究

一种新的低温苯加氢催化剂Ru(Sch iff-base)金属配合物,通过自由配体法封装于Y型沸石的孔腔中。使用XRD、N2吸附、FT-IR、DRS、DTA对催化剂进行表征。结果表明,复合催化剂中希夫碱(Sch iff-base)配体改变了中心离子的电子结构,使其更容易与反应物分子形成配位过渡态,络合活化的反应物分子更容易转化为产物。与离子交换法制备的母体Ru/Y相比,对纯苯的催化加氢性能明显提高。希夫碱配体的几何尺寸对复合材料的催化性能也有很大影响。