לוח שנה משולב

Light-absorbing organic aerosol commonly termed as Brown carbon (BrC) is a significant contributor to radiative forcing of the Earth’s climate and also is of toxicological concern. Understanding the environmental effects of BrC, its sources, formation, and aging processes requires fundamental knowledge of its chromophores and characterization of their light-absorption properties. This seminar will highlight our recent analytical chemistry developments and applications in the area of molecular-level characterization of BrC that provided first insights into diverse composition and properties of its common chromophores. We present the chemical analysis of chromophores reported in a number of case studies of BrC materials associated with emissions from biomass burning and anthropogenic secondary organic aerosols. The results show that BrC chromophores include organic molecules with various structures, polarities, and volatilities. Understanding their chemical identity requires multi-modal analysis employing complementary separation and ionization approaches in combination with high resolution mass spectrometry. These studies allow assessment of BrC optical properties and relating them to fractional contributions from different classes of chromophores such as aromatic carboxylic acids, nitro-phenols; substituted, heterocyclic and pure polycyclic aromatic hydrocarbons.

A new analytical tool for protein characterization that combines the high resolution ion exchange (IEX) chromatography method for protein separation, with multi-angle light scattering (MALS). MALS coupled with size exclusion chromatography (SEC-MALS) is a standard and common method for characterizing protein mass, shape, aggregation, oligomerization, interactions and purity. The limited resolution of SEC interferes in some cases with the accurate analysis that can be achieved by MALS. These include mixtures of protein populations with identical or very similar masses, oligomers with poor separation and small peptides. Here we show that combining MALS with the higher resolution separation technique IEX (IEX-MALS) allows a precise analysis of samples that cannot be resolved by SEC-MALS. We conclude that IEX-MALS is a valuable technique for protein characterization, especially for proteins that have limited analysis achieved with SEC-MALS.