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141.
142.
葡聚糖为载体的双亲型LDL吸附剂吸附动力学研究 总被引:3,自引:0,他引:3
合成了以葡聚为载体,同时具有亲水性磺酸基和疏水性胆固醇两类配基的新型低密度脂蛋白(LDL)吸附剂。通过对LDL纯溶液中吸附等温线的测试,比较了以Dextran G-75为载体的双亲型LDL吸附剂与单一亲水型磺酸基配基,单一疏水型胆固醇基吸附剂吸附量和亲和吸附系数的关系。对双亲型LDL吸附剂的吸附动力学进行了初步研究,在LDL溶液中,亲水型磺酸基,疏水型胆固醇配基,双亲型LDL吸附剂对LDL的吸附曲线基本上符合Langmuir吸附方程,另外通过高离子强度NaCl洗脱实验,测定了双亲型LDL吸附剂上具有的磺酸基与胆固醇两类基在对低密脂蛋白吸附过程中所起的配合效果,为下一步作用力机制研究提供了参考依据。 相似文献
143.
Chun-Long?Chen Andrea?M.?Goforth Mark?D.?Smith William?R.?Gemmill Cheng-Yong?Su Hans-Conrad?zur?LoyeEmail author 《Journal of Cluster Science》2005,16(4):477-487
A new flexible ligand, 1,5-bis(8-oxaquinoline)-3-methylpentane (C5MeOQ), was synthesized and used in the preparation of the
new dinuclear copper(II) complex 1: [Cu2(μ-OMe)2(μ-C5MeOQ)(NO3)2]. Single crystal X-ray analysis revealed that complex 1 contains dinuclear Cu(II) units with bridging methoxo groups. The ligand, C5MeOQ, takes on a bent conformation in order to
connect to and complete the square planar coordination environment of both copper centers; and one of the two Cu(II) centers
adopts a distorted square planar configuration as a result of the ligand conformation. The magnetic properties of complex
1 were investigated by variable-temperature magnetic susceptibility measurements in the 100–300 K range. Interestingly, the
susceptibility data for complex 1 reveals that the compound is diamagnetic, suggesting the presence of very strong antiferromagnetic coupling interactions
between the adjacent Cu(II) centers. 相似文献
144.
An increasing number of docking/scoring programs are available that use different sampling and scoring algorithms. A reliable scoring function is the crucial element of such approaches. Comparative studies are needed to evaluate their current capabilities. DOCK4 with force field and PMF scoring as well as FlexX were used to evaluate the predictive power of these docking/scoring approaches to identify the correct binding mode of 61 MMP-3 inhibitors in a crystal structure of stromelysin and also to rank them according to their different binding affinities. It was found that DOCK4/PMF scoring performs significantly better than FlexX and DOCK4/FF in both ranking ligands and predicting their binding modes. Most notably, DOCK4/PMF was the only scoring/docking approach that found a significant correlation between binding affinity and predicted score of the docked inhibitors. However, comparing only those cases where the correct binding mode was identified (scoring highest among sampled poses), FlexX showed the best `fine tuning' (lowest rmsd) in predicted binding modes. The results suggest that not so much the sampling procedure but rather the scoring function is the crucial element of a docking program. 相似文献
145.
Herein we describe the importance of side chains in C3-symmetric ligands in supramolecular chemistry. The reaction of the new ligand tris(5-bromo-2-methoxybenzylidene)triaminoguanidinium chloride [H3Me3Br3L]Cl (1) with ZnCl2 results in the formation of the monomeric complex (Et3NH)2[(ZnCl2)3Me3Br3L] (2), in which the ligand remains in a conformation less favourable for the coordination of metal centres. The use of the related tris(5-bromo-2-hydroxybenzylidene)triaminoguanidinium chloride, [H6Br3L]Cl, under similar conditions, results in the formation of two different dimeric compounds (NH4)[{[Zn(NH3)]3Br3L}2{mu-(OH)}3]1/4MeOH (3) and [Zn{Zn2(OH2)3(NH3)Br3L}2] (4), depending on the solvent mixture used. The comparable reaction of the ligand tris(5-bromo-2-hydroxy-3-methoxybenzylidene)triaminoguanidinium chloride [H6(OMe)3Br3L]Cl (5), leads to the formation of a doughnut-shaped, protein-sized coordination oligomer (Et3NH)18[{Zn[Zn2Cl{(OMe)3Br3L}]2}6(mu-Cl)6(OH2)6]x CH3CN (6), which comprises six dimeric [Zn5{(OMe)3Br3L}2] units. Whereas 3 and 4 decompose in DMSO solution, 6 is surprisingly stable in the same solvent. 相似文献
146.
Treatment of GaCl3 with one equiv of Li[NC4H3(CH2NMe2)‐2] (n = 1, 2, 3) in diethyl ether at ?78 °C yields GaCl3‐n[NC4H3(CH2NMe2)‐2]n (n = 1, 1 ; n = 2, 2 ; n = 3, 3 ). Compound 1 reacts with two equiv of RLi to afford GaR2[NC4H3(CH2NMe2)‐2] ( 4a, R=Me; 4b, R=Bu ) via transmetallation. Reacting 2 with one equiv of RLi in diethyl ether, 3 and 4 are formed via ligand redistribution. Variable temperature 1H NMR spectroscopic experiments reveal that the five‐coordinate gallium compound 3 is fluxional and results in a coalescence temperature at 5 °C, at which ΔG≠ is calculated at ca. 10.4 Kcal/mole. All the new compounds have been characterized by 1H and 13C NMR spectroscopy and the structures of compounds 3 and 4a have also been determined by X‐ray crystallography. 相似文献
147.
Raymond K. Sheline Harald Mahnke 《Angewandte Chemie (International ed. in English)》1975,14(5):314-321
It has been proven qualitatively by a number of authors using variable temperature NMR experiments that most metal carbonyl complexes are nonrigid. A quantitative determination of the ligand exchange frequency ve is often achieved by a line shape analysis or by measurement of the transverse relaxation time T2 using the Carr-Purcell method. In the case of a “very fast” exchange, however, both methods prove unsuccessful. It is shown in this study that a simultaneous fit of IR or Raman spectra on the one hand and NMR spectra on the other can make possible the determination of ve for the “very fast” exchange and can also facilitate the determination of ve in “slow” and “medium” exchange cases considerably. The ligand exchange frequency thus found for Fe(CO)5, 1.1 × 1010s?1, is unexpectedly high; comparison with variable temperature measurements on solid Fe(CO)5, yields similar energy barriers. A mechanism of exchange closely related to the “Berry mechanism” is proposed. Finally the consequences of this surprisingly large ligand exchange rate are discussed with respect to IR band assignments for molecular “fragments” M(CO)x (where x=coordination number, and M is a transition metal, typically lanthanoid or actinoid). 相似文献
148.
The X-ray crystallographic structure was reported for a dinuclear copper(Ⅱ) complex with a tetraanionic ligand of p-tert-butylsulfonylcalix[4]arene [Cu2L(CH3OH)6]·4CH3OH (H4L=p-tert-butylsuffonylcalix[4]arene). The complex belongs to triclinic system, P1^-- space group, with a = 1.2303(3) nm, b = 1.2377(3) nm, c = 1.3110(3) nm, a =66.862(4)°, β= 67.206(4)°, γ=61.711(3)°, Z= 1, V= 1.5659(7) nm^3, Dc= 1.371 g/cm^3, F(000) = 682,μ(Mo Kα) = 0.883 mm^-1, R1 =0.0325, wR2=0.0870. In this complex, the calix[4]arene acts as a bis-tridentate chelating ligand with the 1,2-alternate conformation. 相似文献
149.
A family of tantalum compounds supported by the triaryloxide [R-L]3− ligands are reported [H3(R-L) = 2,6-bis(4-methyl-6-R-salicyl)-4-tert-butylphenol, where R = Me or tBu]. The reaction of H3[Me-L] with TaCl5 in toluene gave [(Me-L)TaCl2]2 (1). The [tBu-L] analogue [(tBu-L)TaCl2]2 (2) was synthesized via treatment of TaCl5 with Li3[tBu-L]. A THF solution of LiBHEt3 was added to 1 in toluene to provide [(Me-L)TaCl(THF)]2 (3), while treatment of 2 with 2 equiv of LiBHEt3 or potassium in toluene followed by recrystallization from DME resulted in formation of [M(DME)3][{(tBu-L)TaCl}2(μ-Cl)] [M = Li (4a), K (4b)]. When the amount of MBHEt3 (M = Li, Na, K) was increased to 5 equiv, the analogous reactions in toluene afforded [{(bit-tBu-L)Ta}2(μ-H)3M] [M = Li(THF)2 (5a), Na(DME)2 (5b), K(DME)2 (5c)]. During the course of the reaction, the methylene CH activation of the ligand took place. Dissolution of 5a in DME produced [{(bit-tBu-L)Ta}2(μ-H)3Li(DME)2] (6), indicating that the coordinated THF molecules are labile. When the 2/LiBHEt3 reaction was carried out in THF, the ring opening of THF occurred to yield [(tBu-L)Ta(OBun)2]2 (7) along with a trace amount of [Li(THF)4][{(tBu-L)TaCl}2(μ-OBun)] (8). Treatment of 2 with potassium hydride in DME yielded [{(tBu-L)TaCl2K(DME)2}2(μ-OCH2CH2O)] (9), in which the ethane-1,2-diolate ligand arose from partial C-O bond rupture of DME. The X-ray crystal structures of 2, 3, 4, 5a, 6, 7, and 9 are described. 相似文献
150.
Cristina Chamorro 《Tetrahedron》2004,60(39):8691-8697
A large and diverse library of a TAC-based tripodal synthetic receptor library (6) has been prepared by split-mix synthesis on the solid phase. Each receptor of the 46,656-member TAC-based library (6) is attached to a solid support bead and contains three different dipeptide arms. On-bead screening for binding of a d-Ala-d-Ala containing ligand (7) by the TAC-based library (6) was performed in phosphate buffer (0.2 N, pH=7.0). Remarkable selectivity for particular library members was observed. The best binding members from the screening were manually selected using fluorescence microscopy and subjected to structural analysis by sequencing. The thus determined binding sequences showed a high consensus. 相似文献