Stability and Lifetime of Quadruply Hydrogen Bonded 2-Ureido-4[1H]-pyrimidinone Dimers
摘要:
2-Ureido-4[1H]-pyrimidinones are known to dimerize via a strong quadruple hydrogen bond array. A. detailed study of the dimerization constant and lifetime of the dimer is presented here. Excimer fluorescence of pyrene-labeled 2-ureido-4[1H]-pyrimidinone Ib was used to determine a dimerization constant K-dim, of 6 x 10(7) M-1 in CHCl3, 1 x 10(7) M-1 in chloroformsaturated with water, and 6 x 10(8) M-1 in toluene (all at 298 K). Under these conditions, the preexchange lifetime of the similar dimers of both 1d and 1e is 170 ms in CDCl3, 80 ms in wet CDCl3, and 1.7 s in toluene-dp, as determined by dynamic NMR spectroscopy Association rate constants were calculated from the Kdim values and the preexchange lifetimes. The resulting values are significantly lower than the diffusion-controlled association rate constants calculated using the Stokes-Einstein and the Debeije equations. This difference is ascribed to a tautomeric equilibrium of the monomer between the dimerizing 4[1K]-pyrimidinone and nondimerizing 6[1H]-pyrimidinone tautomers, which is unfavorable for dimerization.
Self-Assembly of Ureido-Pyrimidinone Dimers into One-Dimensional Stacks by Lateral Hydrogen Bonding
作者:Marko M. L. Nieuwenhuizen、Tom F. A. de Greef、Rob L. J. van der Bruggen、Jos M. J. Paulusse、Wilco P. J. Appel、Maarten M. J. Smulders、Rint P. Sijbesma、E. W. Meijer
DOI:10.1002/chem.200902107
日期:2010.2.1
with an additional urea functionality self‐assemble into one‐dimensional stacks in various solvents through lateral non‐covalent interactions. 1H NMR and DOSY studies in CDCl3 suggest the formation of short stacks (<10), whereas temperature‐dependent circular dichroism (CD) studies on chiral UPy dimers in heptane show the formation of much larger helical stacks. Analysis of the concentration‐dependent
通过额外的非共价相互作用,被其他尿素官能团取代的Ureido-嘧啶酮(UPy)二聚体在各种溶剂中自组装成一维堆栈。在CDCl 3中的1 H NMR和DOSY研究表明形成了短的烟囱(<10),而对庚烷中手性UPy二聚体的温度依赖性圆二色性(CD)研究表明,形成了更大的螺旋烟囱。CDCl 3中化学位移的浓度依赖性演变分析庚烷中随温度变化的CD效应表明,这种自组装过程在两种溶剂中均遵循等渗途径。聚集体的长度受与脲官能团连接的取代基的影响。与之形成鲜明对比的是,带有一个额外的氨基甲酸酯基团的UPy二聚体不会自组装成有序堆,这从庚烷中不存在CD效应以及CDCl 3中嘧啶酮环的亚烷基质子的浓度无关化学位移可以明显看出。
[n]-Polyurethanes: Synthesis and Characterization
作者:Ron M. Versteegen、Rint P. Sijbesma、E. W. Meijer
DRUG DELIVERY FROM IMPLANTS USING SELF-ASSEMBLED MONOLAYERS-THERAPEUTIC SAMS
申请人:Agrawal C. Mauli
公开号:US20090123516A1
公开(公告)日:2009-05-14
Disclosed are medical devices comprising one or more surfaces, one or more SAM molecules attached to the one or more surfaces of the medical device, and one or more therapeutic agents attached to the one or more self-assembled monolayer molecules. Also disclosed are medical devices comprising one or more surfaces, one or more self-assembled monolayer molecules attached to the one or more surfaces of the medical device, one or more linkers comprising a first functional group and a second functional group, the first functional group attached to the self-assembled monolayer molecule and a therapeutic agent attached to the second functional group. The therapeutic agent may be attached to the SAM molecule via a linker. The present invention also concerns methods of administering a therapeutic agent to a subject, comprising contacting the subject with one of the medical devices set forth herein.
POLYSILOXANE-GRAFTED POLYIMIDE RESIN COMPOSITION AND APPLICATIONS THEREOF
申请人:CHI MEI CORPORATION
公开号:US20130109803A1
公开(公告)日:2013-05-02
A polysiloxane-grafted polyimide resin composition includes a polysiloxane-grafted polyimide resin, and a solvent. The polysiloxane-grafted polyimide resin is represented by formula (I):
wherein
W represents a tetravalent organic group,
R represents a trivalent organic group, and
X represents a polysiloxane-containing group.
POLYSILOXANE-GRAFTED POLYIMIDE RESIN COMPOSITION AND FLEXIBLE SUBSTRATE MADE THEFEFROM
申请人:CHI MEI CORPORATION
公开号:US20130267651A1
公开(公告)日:2013-10-10
A polysiloxane-grafted polyimide resin composition includes a polysiloxane-grafted polyimide resin, and a solvent. The polysiloxane-grafted polyimide resin is represented by Formula (I):
wherein
W represents a tetravalent organic group,
R represents a trivalent organic group, and
X
1
and X
2
independently represent a polysiloxane-containing group.