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Hydrophilic Interaction (hydrophilic + interaction)
Terms modified by Hydrophilic Interaction Selected AbstractsHydrophilic interaction and reversed-phase ultra-performance liquid chromatography TOF-MS for metabonomic analysis of Zucker rat urineJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2008Helen G. Gika Abstract Hydrophilic interaction chromatography (HILIC) provides a complementary technique to RP methods for the retention of polar analytes for LC-MS-based metabonomic studies. Combining the advantages of both RP and HILIC separations with the efficient and rapid separations obtained using sub-2 ,m particles via the recently introduced ultra-performance LC (UPLC) enables increased coverage of the metabolites present in biological samples to be achieved. Here an HILIC-UPLC-MS method was developed to provide metabolite profiles for urine samples obtained from male Zucker rats. The resulting data were compared with results obtained for the same samples by RP-UPLC-MS and demonstrated the complementary nature of the two separations with both methods enabling discrimination between the different sample types. Interestingly sample type differentiation was based on different markers. [source] Methacrylate-based monolithic column with mixed-mode hydrophilic interaction/strong cation-exchange stationary phase for capillary liquid chromatography and pressure-assisted CECELECTROPHORESIS, Issue 19 2008Jian Lin Abstract A novel porous polymethacrylate-based monolithic column by in situ copolymerization of 3-sulfopropyl methacrylate (SPMA) and pentaerythritol triacrylate in a binary porogenic solvent consisting of cyclohexanol/ethylene glycol was prepared. The monolith possessed in their structures bonded sulfonate groups and hydroxyl groups and was evaluated as a hydrophilic interaction and strong cation-exchange stationary phases in capillary liquid chromatography (cLC) and pressure-assisted CEC using small polar neutral and charged solutes. While the SPMA was introduced as multifunctional monomer, the pentaerythritol triacrylate was used to replace ethylene glycol dimethacrylate as cross-linker with much more hydrophilicity due to a hydroxyl sub-layer. The different characterization of monolithic stationary phases were specially designed and easily prepared by altering the amount of SPMA in the polymerization solution as well as the composition of the porogenic solvent for cLC and pressure-assisted CEC. The resulting monolith showed the different trends about the effect of the permeabilities on efficiency in the pressure-assisted CEC and cLC modes. A typical hydrophilic interaction chromatography mechanism was observed at higher organic solvent content (ACN%>70%) for polar neutral analytes. For polar charged analytes, both hydrophilic interaction and electrostatic interaction contributed to their retention. Therefore, for charged analytes, selectivity can be readily manipulated by changing the composition of the mobile phase (e.g., pH, ionic strength and organic modifier). With the optimized monolithic column, high plate counts reaching greater than 170,000,plates/m for pressure-assisted CEC and 105,000 plates/m for cLC were easily obtained, respectively. [source] Separation and determination of five major opium alkaloids with mixed mode of hydrophilic/cation-exchange monolith by pressurized capillary electrochromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2007Xucong Lin Abstract A method for the separation and determination of five major opium alkaloids (narcotine, papaverine, thebaine, codeine, and morphine) in pericarpium papaveris by pressurized CEC (pCEC) with monolithic column has been developed. Under the optimum condition, linear calibration ranges of narcotine, papaverine, thebaine, codeine, and morphine were obtained as 2,85, 2,85, 5,75, 10,65, and 10,65 ,g/mL, respectively. LODs of these analytes were 1.5,6.0 ,g/mL. The RSD (n = 7) of the migration time and peak area were 1.94,5.24 and 4.05,8.21%, respectively. The proposed method was successfully applied to the analysis of pericarpium papaveris samples. Average recoveries of 79.0,95.9% at different fortified levels of alkaloids were achieved with RSD less than 4.6%. Meanwhile, the mechanism of the separation of the alkaloids on the monolithic column was also discussed. The result showed that the separation of alkaloids was mainly based on the mixed mode of hydrophilic interaction (HI) and cation exchange. [source] Calculation of relative binding affinities of fructose 1,6-bisphosphatase mutants with adenosine monophosphate using free energy perturbation methodJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2007Ravichandra Mutyala Abstract The free energy perturbation (FEP) methodology is the most accurate means of estimating relative binding affinities between inhibitors and protein variants. In this article, the importance of hydrophobic and hydrophilic residues to the binding of adenosine monophosphate (AMP) to the fructose 1,6-bisphosphatase (FBPase), a target enzyme for type-II diabetes, was examined by FEP method. Five mutations were made to the FBPase enzyme with AMP inhibitor bound: 113Tyr , 113Phe, 31Thr , 31Ala, 31Thr , 31Ser, 177Met , 177Ala, and 30Leu , 30Phe. These mutations test the strength of hydrogen bonds and van der Waals interactions between the ligand and enzyme. The calculated relative free energies indicated that: 113Tyr and 31Thr play an important role, each via two hydrogen bonds affecting the binding affinity of inhibitor AMP to FBPase, and any changes in these hydrogen bonds due to mutations on the protein will have significant effect on the binding affinity of AMP to FBPase, consistent to experimental results. Also, the free energy calculations clearly show that the hydrophilic interactions are more important than the hydrophobic interactions of the binding pocket of FBPase. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Atypical polysaccharide physical gels: structure/property relationshipsMACROMOLECULAR SYMPOSIA, Issue 1 2003Alexandra Clayer Abstract Chitin and chitosan are polysaccharides produced by the biomass. They have the same general chemical structure and constitute the series of linear copolymers of linked ,, (1->4) glucosamine and N-actylglucosamine. We studied the possibility of forming physical gels with all the terms of this series, whatever the proportion of the two kinds of residues included in the polymer chains. We show that physical gelation is still possible through a percolating process when certain important conditions are met. Initially the concentration in polymer must be above C*; a critical value of the balance between hydrophobic and hydrophilic interactions must be achieved and gelation must occur simultaneously everywhere in the medium. These conditions were observed in several situations allowing the formation of different kinds of gels at all values of DA. In view of the rare bio-active properties of chitin and chitosan, these gels were tested for living tissue regeneration and constitute very interesting examples in illustration of our concept of decoys for biological media. [source] Proteolytically Degradable Photo-Polymerized Hydrogels Made From PEG,Fibrinogen Adducts,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Daniel Dikovsky Abstract We develop a biomaterial based on protein,polymer conjugates where poly(ethylene glycol) (PEG) polymer chains are covalently linked to multiple thiols on denatured fibrinogen. We hypothesize that conjugation of large diacrylate-functionalized linear PEG chains to fibrinogen could govern the molecular architecture of the polymer network via a unique protein,polymer interaction. The hypothesis is explored using carefully designed shear rheometry and swelling experiments of the hydrogels and their precursor PEG/fibrinogen conjugate solutions. The physical properties of non-cross-linked and UV cross-linked PEGylated fibrinogen having PEG molecular weights ranging from 10 to 20,kDa are specifically investigated. Attaching multiple hydrophilic, functionalized PEG chains to the denatured fibrinogen solubilizes the denatured protein and enables a rapid free-radical polymerization cross-linking reaction in the hydrogel precursor solution. As expected, the conjugated protein-polymer macromolecular complexes act to mediate the interactions between radicals and unsaturated bonds during the free-radical polymerization reaction, when compared to control PEG hydrogels. Accordingly, the cross-linking kinetics and stiffness of the cross-linked hydrogel are highly influenced by the protein,polymer conjugate architecture and molecular entanglements arising from hydrophobic/hydrophilic interactions and steric hindrances. The proteolytic degradation products of the protein,polymer conjugates proves to be were different from those of the non-conjugated denatured protein degradation products, indicating that steric hindrances may alter the proteolytic susceptibility of the PEG,protein adduct. A more complete understanding of the molecular complexities associated with this type of protein-polymer conjugation can help to identify the full potential of a biomaterial that combines the advantages of synthetic polymers and bioactive proteins. [source] | |||||||||||||