Chemical modifications can potentially induce conformational changes near the modification site and thereby impact the safety and efficacy of protein therapeutics. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) has emerged as a powerful analytical technique with high spatial resolution and sensitivity in detecting such local conformational changes. In this study, we utilized HDX-MS combined with structural modeling to examine the conformational impact on monoclonal antibodies (mAbs) caused by common chemical modifications including methionine (Met) oxidation, aspartic acid (Asp) isomerization, and asparagine (Asn) deamidation. Four mAbs with diverse sequences and glycosylation states were selected. The data suggested that the impact of Met oxidation was highly dependent on its location and glycosylation state. For mAbs with normal glycosylation in the Fc region, oxidation of the two conserved Met252 and Met428 (Kabat numbering) disrupted the interface interactions between the CH2 and CH3 domains, thus leading to a significant decrease in CH2 domain thermal stability as well as a slight increase in aggregation propensity. In contrast, Met oxidation in the variable region and CH3 domain had no detectable impact on mAb conformation. For aglycosylated mAb, Met oxidation could cause a more global conformational change to the whole CH2 domain, coincident with the larger decrease in thermal stability and significant increase in aggregation rate. Unlike Met oxidation, Asn deamidation and Asp isomerization mostly had very limited effects on mAb conformation, with the exception of succiminide intermediate formation which induced a measurable local conformational change to be more solvent protected. Structural modeling suggested that the succinimide intermediate was stabilized by adjacent aromatic amino acids through ring-ring stacking interactions.

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und on the face. He had had no vomiting, no pain in the hack, and only slight anorexia and pyrexia. Whatever it was, I decided to watch and isolate him as best I could in the steerage, wich oarbolised sheets. A small wooden structure on deck was already full with cases of measles, and in 'winter one cannot u!-e boats for isolation. On arrival, the chip was detained by the quarantine authorities, experts from the city were consulted, who discussed and differed, and after four days we were allowed to proceed up the river. The man was placed in a ftver hospital, and the immigrants vaccinated by me had permission to land. The others, who all had recent vaccination certificates, were sentenced, poor healthy-6oulii, to fourteen days' imprisonment. No smallpox occurred subsequently. During another voyage there was a case of chicken-pox about which I had no doubt at all. A child developed rosy papules, which rapidly became globular, ' , gradually enlarging, unicellular vesicles surrounded by pink-' , red ajeolas fresh crops following the first. We passed quaran-' , tine, but on docking a health officer came on board. He saw ' , he case in the stage most difficult to diagnose-when the ' , vesicles were dried up and scabbing-and unhesitatingly pronounced it to be smallpox. I handed him my medical log. He only smiled pragmatically and pointed to the eruption Luckily for us, though, a senior medical man judged the case, with a verdict for varice la. I am, Sirs, yours faithfully, Brighton, Jan. 17th, 1894.