Time Window Expansion for HDX Analysis of an Intrinsically Disordered Protein

Application of typical HDX methods to examine intrinsically disordered proteins (IDP), proteins that are natively unstructured and highly dynamic at physiological pH, is limited because of the rapid exchange of unprotected amide hydrogens with solvent. The exchange rates of these fast exchanging amides are usually faster than the shortest time scale (10 s) employed in typical automated HDX-MS experiments. Considering the functional importance of IDPs and their association with many diseases, it is valuable to develop methods that allow the study of solution dynamics of these proteins as well as the ability to probe the interaction of IDPs with their wide range of binding partners. Here, we report the application of time window expansion to the millisecond range by altering the on-exchange pH of the HDX experiment to study a well-characterized IDP; the activation domain of the nuclear receptor coactivator, peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α). This method enabled mapping the regions of PGC-1α that are stabilized upon binding the ligand binding domain (LBD) of the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ). We further demonstrate the method’s applicability to other binding partners of the IDP PGC-1α and pave the way for characterizing many other biologically important ID proteins.

Mechanism of and Products from the Oxidation of Phenols by Hypervalent Iodine Compounds

Iodobenzene dichloride or diacetate initiates the polymerization of 2,6-dimethylphenolate anion to poly [oxy(2,5-dimethyl)-l, 4-phenylene]. Electron spin resonance spectroscopy was used to identify the polymeric radical that is the growing chain. Infrared and NMR spectroscopy identified the final polymer. The mechanism proposed is probably applicable also to other phenol oxidation processes yielding substituted poly(oxyphenylenes).

The anomalous chemistry of those compounds of xenon, iodine, and tellurium in which the number of bonding electrons exceeds that given by Lewis valence theory has been considered in general terms by Musher [1] who coined the term “hypervalent” to describe these substances. The oxidizing properties of these compounds is in a general way similar to that of peroxides and other strong oxidizing agents, but has not been characterized in any exact fashion. We have observed [2] that the iodobenzene esters have polymeric analogs of the formula, [-I(R)OOCXCOO-], and these compounds are stable oxidizing agents (R = aryl; X = alkylene or arylene). We have been interested in determining if -I(R)OXO- compounds can be formed.

The first question to consider is the stability of bonds in -OI(R)O- compounds. Only acyl derivatives are known [3]. However, the possibility     

Production of Polymers from the Seed Oil of Crambe Abyssinica. III. Polyurethane Elastomers Based on Tridecanedioic (Brassylic) Acid

A series of predominately hydroxyl-ended polyesters were made from tridecanedioic acid derived from crambe oil. Comparison materials with sebacic and adipic acids were also prepared. Suitable polyesters were converted into polyurethane elastomers by chain extension and cross-linking with a diisocyanate and further diol. Polyesters based on ethandiol were unsuitable for the production of flexible urethanes as a slow crystallization occurred on standing; this did not happen when mixed ethane- and propan-diols were employed in polyesterification. Polyurethanes based on diphenylmethane diisocyanate are stronger than those made with the mixed isomers of toluene diisocyanate. Polyurethane networks based on brassylic acid have a lower     

Polymeric Schiff Bases. VI. The Direct Syntheses of Poly-Schiff Bases

The synthesis of black, high molecular weight polymeric Schiff bases directly from aryldiamines and aryldialdehydes by two methods is described. The first method utilizes benzylideneaniline as the reaction medium. The second method is a direct one-step synthesis involving the reaction of the aryldiamine, aryldialdehyde, aniline, and benzaldehyde. The thermogravimetric analyses of the polymers thus prepared compared favorably with similar polymers prepared by the bis-Schiff base exchange method.     

Photopolymerization of Methyl Acrylate in Dimethyl Sulfoxide

Abstract

Methyl acrylate in dimethyl sulfoxide was polymerized by 2537 A ultraviolet light. The photo reaction exhibited zero-order kinetics for a given initial concentration and produced short chain polymers (M[Mbar]_W ～ 20,000). Low sulfur values of isolated polymers indicated no appreciable solvent incorporation during the polymerization.     

Polymer Intermediates and Polymers Derived from 5-t-Butyl-m-Xylene

Abstract

A series of condensation polymer intermediates, which included several new compositions, was prepared from 5-t-butyl-m-xylene (I) so that the effect of the bulky t-butyl group on polymer properties could be determined. Compound (I) was oxidized with nitric acid to obtain 5-t-butyl-isophthalic acid (II), which was converted successively to the diacid chloride, the diamide, the dinitrile, and finally to 5-t-butyl-m-xylene-α,α′-diamine (VI); the overall yield was 80%. The dimethyl ester of (II) was prepared and converted to 5-t-butyl-m-xylene-α,α′-diol (VIII), a new composition, in 79.5% overall yield; the diphenyl ester was also prepared. The sodium salt of (II) was catalytically reduced to obtain 5-t-butyl-1,3-cyclohexanedicarboxylic acid (IIa) in 95% yield. (IIa) was converted successively to the diacid chloride, the diamide, the dinitrile, and finally to 5-t-butyl-1,3-cyclohexanebis(methylamine) (VIa), a new composition; the overall yield was 37%. (IIa) was also converted to the dimethyl ester and finally to 5-t-butyl-1,3-cyclohexanedimethanol (VIIIa), a new composition; the overall yield was 64%. Condensation polymers were prepared from the intermediates (II), (IIa), (VI), (VIa), (VIII), and (VIIIa). These polymers had higher glass transition temperatures (T_g) than corresponding polymers containing no t-butyl groups. This general effect of the t-butyl group to increase the T_g value of the polymer was noted in all polymers prepared, regardless of whether the intermediate carrying the t-butyl group was a diacid, a diol, or a diamine, or whether the polymer was a polyamide, a polyester, or a polyurethane.     

Synthesis of New Polyphosphazenes. The Reactions of Poly(dichlorophosphazene) with Aminotetraalkoxycyclotriphosphazene and Sodium Phenoxide

Abstract

A new poly(organophosphazenes) copolymer was formed from the reaction of aminopentafluoroethoxycyclotriphosphazene, sodium phenoxide, and poly(dichlorophosphazene). The polymer was thermoplastic and the T_g increased with an increasing amount of the phenol group. The T_g of the polymer with aminopentafluoroethoxycyclotriphosphazene attached as a pendant group was similar to the T_g of polyfluoroethoxyphosphazene.     

Hexavalent Chromium-Thioacetamide Redox System Initiated Polymerization of Acrylonitrile

Polymerization of acrylonitrile initiated by the Cr⁶⁺/thioacetamide redox system was studied in nitrogen atmosphere in the temperature range 35–45°C. The rate of polymerization and the rate of Cr⁶⁺ ion disappearance were measured. The effect of certain water-miscible organic solvents, neutral electrolytes, and complexing agents on the rate of polymerization was investigated. Chromic acid alone did not initiate the polymerization under deaerated and undeaerated conditions. Depending on the results obtained, a suitable kinetic scheme was proposed and various rate parameters were evaluated.     

Influence of Monomer and Initiator Concentrations on the Simultaneous Grafting of Several Monomers onto Insoluble Collagen

Simultaneous grafting of 2-hydroxyethyl methacrylate and methyl methacrylate (3:1 and 3:2 mole ratios) onto insoluble collagen with ceric ammonium nitrate as initiator was attempted with a view to optimizing conditions for the preparation of hydrogels. The influence of monomer and initiator concentrations on the grafting reactions was investigated. The grafting results are discussed in the light of grafting efficiency and percentage of grafting. They were found to be lower when the 3:1 mole ratio of monomers was used.