Tyrosine nitration of human ERK1 introduces an intra-hydrogen bond by molecular dynamics simulations

Structural Chemistry - ERK1 is an important kinase in Ras–Raf–MEK signaling. We have recently demonstrated by mass spectrometry that Tyr210 of ERK1 can be nitrated, and the nitration...     

Weak closure and Oliver’s p-group conjecture

To date almost all verifications of Oliver’s p-group conjecture have proceeded by verifying a stronger conjecture about weakly closed quadratic subgroups. We construct a group of order 3⁴⁹ which refutes the weakly closed conjecture but satisfies Oliver’s conjecture.     

Complementary MS Methods Assist Conformational Characterization of Antibodies with Altered S–S Bonding Networks

As therapeutic monoclonal antibodies (mAbs) become a major focus in biotechnology and a source of the next-generation drugs, new analytical methods or combination methods are needed for monitoring changes in higher order structure and effects of post-translational modifications. The complexity of these molecules and their vulnerability to structural change provide a serious challenge. We describe here the use of complementary mass spectrometry methods that not only characterize mutant mAbs but also may provide a general framework for characterizing higher order structure of other protein therapeutics and biosimilars. To frame the challenge, we selected members of the IgG2 subclass that have distinct disulfide isomeric structures as a model to evaluate an overall approach that uses ion mobility, top-down MS sequencing, and protein footprinting in the form of fast photochemical oxidation of proteins (FPOP). These three methods are rapid, sensitive, respond to subtle changes in conformation of Cys?→?Ser mutants of an IgG2, each representing a single disulfide isoform, and may be used in series to probe higher order structure. The outcome suggests that this approach of using various methods in combination can assist the development and quality control of protein therapeutics.      

Novel Copolymers of Styrene. 15. Phenoxy Ring-Substituted Methyl 2-Cyano-3-Phenyl-2-Propenoates

Electrophilic trisubstituted ethylenes, phenoxy ring-substituted methyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO₂CH₃, where R is 4-(4-BrC₆H₅O), 2-(4-ClC₆H₅O), 3-(4-ClC₆H₅O), 4-(3-ClC₆H₅O), 4-(4-ClC₆H₅O), 4-(4-FC₆H₅O), 2-(3-CH₃OC₆H₅O), 2-(4-CH₃OC₆H₅O), 3-(4-CH₃OC₆H₅O), 4-(4-CH₃OC₆H₅O), 3-(4-CH₃C₆H₅O) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of phenoxy ring-substituted benzaldehydes and methyl cyanoacetate, and characterized by CHN analysis, IR, ¹H and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, ¹H and ¹³C-NMR. The order of relative reactivity (1/r₁) for the monomers is 4-(4-CH₃OC₆H₅O) (6.07) > 3-(4-ClC₆H₅O) (3.38) > 3-(4-CH₃OC₆H₅O) (2.78) > 4-(3-ClC₆H₅O) (2.77) > 2-(4-ClC₆H₅O) (2.29) > 3-(4-CH₃C₆H₅O) (1.98) > 4-(4-FC₆H₅O) (1.92) > 4-(4-ClC₆H₅O) (1.89) > 2-(3-CH₃OC₆H₅O) (1.39) > 2-(4-CH₃OC₆H₅O) (0.90) > 4-(4-BrC₆H₅O) (0.77). Relatively high T_g of the copolymers in comparison with that of polystyrene indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200-500°C range with residue (2.5-8.0% wt), which then decomposed in the 500-800°C range.