Impact of ionic strength on adsorption capacity of chromatographic particles employed in separation of monoclonal antibodies

The influence of ionic strength on the adsorption capacity of seven commercial adsorbents used in downstream processing of monoclonal antibodies was examined. Affinity (MabSelect, Poros 50A High Capacity, ProSep-vA High Capacity), hydrophobic charge-induction (MEP HyperCel), and cation exchange adsorbents (FractoGel EMD SE Hicap (M), SP Sepharose Fast Flow, Ceramic HyperD F) were used to study the adsorption of polyclonal human immunoglobulin G at optimal pH values. The ionic strength, adjusted by sodium chloride concentrations in the range of 0–225 mM, strongly decreased the adsorption capacity of the cation exchangers. Equilibrium data were described in the form of the dependence of the ratio of protein concentrations in the solid and liquid phases on the total concentration of cation counter ions. They were successfully fitted and interpreted through a stoichiometric ion-exchange model.     

Modulation of Living Cell Behavior with Ultra‐Low Fouling Polymer Brush Interfaces

Ultra‐low fouling and functionalizable coatings represent emerging surface platforms for various analytical and biomedical applications such as those involving examination of cellular interactions in their native environments. Ultra‐low fouling surface platforms as advanced interfaces enabling modulation of behavior of living cells via tuning surface physicochemical properties are presented and studied. The state‐of‐art ultra‐low fouling surface‐grafted polymer brushes of zwitterionic poly(carboxybetaine acrylamide), nonionic poly(N‐(2‐hydroxypropyl)methacrylamide), and random copolymers of carboxybetaine methacrylamide (CBMAA) and HPMAA [p(CBMAA‐co‐HPMAA)] with tunable molar contents of CBMAA and HPMAA are employed. Using a model Huh7 cell line, a systematic study of surface wettability, swelling, and charge effects on the cell growth, shape, and cytoskeleton distribution is performed. This study reveals that ultra‐low fouling interfaces with a high content of zwitterionic moieties (>65 mol%) modulate cell behavior in a distinctly different way compared to coatings with a high content of nonionic HPMAA. These differences are attributed mostly to the surface hydration capabilities. The results demonstrate a high potential of carboxybetaine‐rich ultra‐low fouling surfaces with high hydration capabilities and minimum background signal interferences to create next‐generation bioresponsive interfaces for advanced studies of living objects.     

pH‐ and temperature‐sensitive statistical copolymers poly[2‐(dimethylamino)ethyl methacrylate‐stat‐2‐vinylpyridine] with Functional succinimidyl‐ester chain ends synthesized by nitroxide‐mediated polymerization

Statistical copolymerizations of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) with 2‐vinylpyridine (2VP) with 80 to 99 mol % DMAEMA in the feed utilizing a succinimidyl ester‐terminated alkoxyamine unimolecular initiator (NHS‐BlocBuilder) at 80 °C in bulk were performed. The effectiveness of 2VP as a controlling comonomer is demonstrated by linear increases in number‐average molecular weight versus conversion, relatively low PDI (1.5–1.6 with up to 98% DMAEMA) and successful chain extensions with 2VP. Additional free nitroxide does not significantly improve control for the DMAEMA/2VP copolymerizations. The succinimidyl ester on the initiator permits coupling to amine‐terminated poly(propylene glycol) (PPG), yielding an effective macroinitiator for synthesizing a doubly thermo‐responsive block copolymer of PPG‐block‐P(DMAEMA/2VP). A detailed study of the thermo‐ and pH‐sensitivities of the statistical and block copolymers is also presented. The cloud point temperature of the statistical copolymers is fine tuned from 14 to 75 °C by varying polymer composition and pH. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012.     

Perindoprilat monohydrate

The title compound [systematic name: (1S)‐2‐((S)‐{1‐[(2S,3aS,7aS)‐2‐carboxyoctahydro‐1H‐indol‐1‐yl]‐1‐oxopropan‐2‐yl}azaniumyl)pentanoate monohydrate], C₁₇H₂₈N₂O₅·H₂O, (I)·H₂O, the active metabolite of the antihypertensive and cardiovascular drug perindopril, was obtained during polymorphism screening of perindoprilat. It crystallizes in the chiral orthorhombic space group P2₁2₁2₁, the same as the previously reported ethanol disolvate [Pascard, Guilhem, Vincent, Remond, Portevin & Laubie (1991). J. Med. Chem. 34 , 663–669] and dimethyl sulfoxide hemisolvate [Bojarska, Maniukiewicz, Sieroń, Fruziński, Kopczacki, Walczyński & Remko (2012). Acta Cryst. C 68 , o341–o343]. The asymmetric unit of (I)·H₂O contains one independent perindoprilat zwitterion and one water molecule. These interact via strong hydrogen bonds to give a cyclic R²₂(7) synthon, which provides a rigid molecular conformation. The geometric parameters of all three forms are similar. The conformations of the perhydroindole group are almost identical, but the n‐alkyl chain has conformational freedom. A three‐dimensional hydrogen‐bonding network of O—H...O and N—H...O interactions is observed in the crystal structure of (I)·H₂O, similar to the other two solvates, but because of the presence of different solvents the three crystal structures have diverse packing motifs. All three solvatomorphs are additionally stabilized by nonclassical weak C—H...O contacts.