To investigate quantitatively the cooperative binding ability of β-cyclodextrin dimers, a series of bridged bis(β-cyclodextrin)s with 2,2'-diselenobis(benzoyl) spacer connected by different lengths of oligo(ethylenediamine)s (2−5) and their platinum(IV) complexes (6−9) have been synthesized and their inclusion complexation behavior with selected substrates, such as Acridine Red, Neutral Red, Brilliant Green, Rhodamine B, ammonium 8-anilino-1-naphthalenesulfonate, and 6-p-toluidino-2-naphthalenesulfonic acid, were investigated by means of ultraviolet, fluorescence, fluorescence lifetime, circular dichroism, and 2D-NMR spectroscopy. The spectral titrations have been performed in aqueous phosphate buffer solution (pH 7.20) at 25 °C to give the complex stability constants (KS) and Gibbs free energy changes (−ΔG°) for the inclusion complexation of hosts 2−9 with organic dyes and other thermodynamic parameters (ΔH° and TΔS°) for the inclusion complexation of 2−5 with fluorescent dyes ANS and TNS. The results obtained indicate that β-cyclodextrin dimers 2−5 can coordinate with one or two platinum(IV) ions to form 1:1 or 1:2 stoichiometry metallobridged bis(β-cyclodextrin)s. As compared with parent β-cyclodextrin (1) and bis(β-cyclodextrin)s 2−5, metallobridged bis(β-cyclodextrin)s 6−9 can further switch the original molecular binding ability through the coordinating metal to orientate two β-cyclodextrin cavities and an additional binding site upon the inclusion complexation with model substrates, giving the enhanced binding constants KS for both ANS and TNS. The tether length between two cyclodextrin units plays a crucial role in the molecular recognition with guest dyes. The binding constants for TNS decrease linearly with an increase in the tether length of dimeric β-cyclodextrins. The Gibbs free energy change (−ΔG°) for the unit increment per ethylene is 0.32 kJ·mol-1 for TNS. Thermodynamically, the higher complex stabilities of both ANS and TNS upon the inclusion complexation with 2−5 are mainly contributed to the favorable enthalpic gain (−ΔH°) by the cooperative binding of one guest molecule in the closely located two β-cyclodextrin cavities as compared with parent β-cyclodextrin. The molecular binding ability and selectivity of organic dyes by hosts 1−9 are discussed from the viewpoints of the multiple recognition mechanism and the size/shape-fitting relationship between host and guest.
Vein patterns have been used in commercial biometric systems for many years and are recently considered for criminal authentication. Understanding the similarity between genetically identical vein patterns is important, especially when using them in legal cases involving identical twins. Vein patterns sharing the same Deoxyribonucleic acid (DNA) sequence are generally regarded as vein patterns with maximum similarity. If they are completely distinguishable, it implies that the uniqueness of vein patterns is high. Though the genetic dependence of other biometric traits, including fingerprints, faces, palmprints, and irises, have been studied, genetically identical vein patterns have not been studied systematically. With the help of an automatic vein pattern matching algorithm, this paper analyzes and measures the similarity between genetically identical vein patterns. 234 genetically identical forearm pairs and 204 genetically identical thigh pairs were collected for this study. Experimental results indicate that genetically identical vein patterns have extra similarity, but they are distinguishable.
Two β-cyclodextrin derivatives with chiral chromophoric substituents, that is, l- (1) and d-tyrosine-modified β-cyclodextrin (2), were synthesized and fully characterized. Their inclusion modes, binding abilities, and molecular selectivities with four steroid guests, that is, cholic acid sodium salt (CA), deoxycholic acid sodium salt (DCA), glycochoic acid sodium salt (GCA), and taurocholic acid sodium salt (TCA), were investigated by the circular dichroism, 2D NMR, and isothermal titration microcalorimetry (ITC). The results obtained from the circular dichroism and 2D NMR showed that two hosts adopted the different binding geometry, and these differences subsequently resulted in the significant differences of molecular binding abilities and selectivities. As compared with native β-cyclodextrin and tryptophan-modified β-cyclodextrin, host 2 showed the enhanced binding abilities for CA and DCA but the decreased binding abilities for GCA and TCA; however, host 1 showed the decreased binding abilities for all four bile salts. The best guest selectivity and the best host selectivity were KS2-DCA/KS2-TCA = 12.6 and KS2-CA/KS1-CA = 10, respectively, both exhibiting great enhancement as compared with the corresponding values of the previously reported l- and d-tryptophan-modified β-cyclodextrins. Thermodynamically, it was the favorable enthalpic gain that led to the high guest selectivity and host selectivity.
[structure: see text] The binding ability and self-assembly behavior of molecular interpenetration by newly synthesized mono[6-O-(4-formyl-phenyl)-beta-cyclodextrin has been investigated, revealing the formation mechanism of modified cyclodextrin from solution aggregation to solid linear polymeric supramolecules.
A simple, accurate and validated reverse-phase high-performance liquid chromatography (HPLC)/UV method is developed for the determination of glucosamine hydrochloride (GlcN), N-acetyl-glucosamine (NAG) and N-acryloyl-glucosamine (AGA) released from photocrosslinked gelatin hydrogels. The HPLC separation was achieved on a Shimadzu InertSustain amino column (250 × 4.6 mm, 5 µm particle size) at room temperature using a mobile phase of acetonitrile-phosphate buffer (75:25, v/v, pH 6.0) at a flow rate of 1.0 mL/min and UV detection of 194 nm. The method was validated for specificity, linearity, limit of detection and quantification, accuracy, precision, extraction recovery and solution stability. The calibration curves were with excellent linearity, with correlation coefficients (R(2)) >0.999 for all three drugs. The intra- and inter-day variation was <3.10% and the relative error was between -1.43 and 1.78%. The extraction recovery results ranged from 94.62 to 99.33%, demonstrating the absence of matrix effect. The sample and standard solutions were stable for more than 2 months. The method was successfully used for the analysis of released properties of drugs physically encapsulated and chemically crosslinked in the gelatin hydrogels.
The article discusses on the development of informatization in China, on basis of analysis of the developing trend of the world's informatization. The article states that the level of informatization development has become an important indicator in measure of the ability of international competitiveness, the degree of modernization, overall national strength and the ability of economic growth of countries and regions. In discussing the characteristics on the development of informatization in China, the article suggests that China put informatization coverage of the overall situation of modernization as a major strategy, the information network already became the important basis facility which the support development of economy and society, the information industry has become a leader in development of the national economy, information technology plays a significant supporting role in various fields of national economic and social development, informatization development environment has been further optimized.
A novel host molecule H(2)1 bearing a dibenzo[24]-crown-8 moiety and a dipicolinic acid group was synthesized, and its Tb(3+) complex displayed a satisfactory luminescent emission. The tris[2]pseudorotaxane formed from [Tb.1(3)](3-) and ferrocene derivative 2 reveals excellent reversible luminescent lanthanide behavior.
Abstract For the problem that the traditional manufacturing method of spacecraft integral panel can not meet the manufacturing precision of the complex lightweight integral panel of the new generation of spacecraft, a method of roll bending in the state of flat plate first and then machining the grid features of the outer surface is proposed. ANSYS is used to simulate and analyze the internal stress when the integral panel with different roll bending radius when fitting with the tooling. It is obtained that it is easier to realize clamping and bonding by controlling the roll bending radius of the integral panel according to the negative difference. The clamping and positioning of the integral panel with vacuum adsorption device and the machining with variable helix angle milling cutter can effectively reduce the machining vibration. Combined with the processing compensation based on detection, the problem of out of tolerance of wall thickness in processing is solved, and finally the consistency of wall thickness is guaranteed. The experimental results show that this method can control the wall thickness of the integral panel within 1.05~1.33mm.
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