We have developed a straight forward method that uses monolayer protected clusters (MPCs) and mixed monolayer protected clusters (MMPCs) as selective extraction and concentration probes for peptides. After extraction with these nanoparticles (NPs), the peptides are analyzed by MALDI-TOF-MS to obtain their mass fingerprints. Application of the method to a test library of 146 tryptic peptides showed that cationic MPCs/MMPCs target negatively charged peptides while the anionic MPCs/MMPCs target positively charged peptides. The extraction with these NPs is also accompanied by high concentration factors such they can be used to extract and concentrate microcystin-LR at levels below the WHO guideline of 1μg/L.

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Small biomolecule systems were interrogated using infrared multiple photon dissociation (IRMPD) action spectroscopy and corresponding quantum chemical calculations with a particular focus on peptide fragmentation and protonation site preference. b2+ and b3+ fragment ions with a terminal lysine homolog residue were investigated using IRMPD in the fingerprint region (1000 cm-1 – 2000 cm-1) and a variety of computational methods. We present the first spectroscopic confirmation of b-ion formation with a lactam structure. Infrared spectra for b2+ fragment system indicate the presence of a mixture of structures, though final determination will require further investigation. The b3+ fragment ion infrared spectra show strong support for the presence of a predominantly lactam structure. Extensive computational research in this system suggests the B3LYP method to be the most computationally efficient density functional theory method for spectral predictions. However, the inclusion of p-polarization into the basis set yielded inconclusive results and should be investigated further.

Complex organic mixtures in the environment can contain hundreds to thousands of different organic molecules, and their composition and reactivity can have important environmental implications. In addition to gases, the atmosphere is made of a variety of small liquids and solids called aerosols. These aerosols have large impacts on human health, climate, and atmospheric chemical reactions. Here, secondary organic aerosol (SOA) from the ozonolysis of α-pinene is characterized. The atmospheric lifetime of SOA is very uncertain, but recent laboratory and modeling studies have demonstrated that photolysis is potentially an important process for organic mass loss from aerosol particles.1-5 Photolysis modifies the molecular composition and properties of aerosols through photolytic cleaving and repartitioning of volatile products. Characterization of dry, irradiated SOA can provide insights into photolysis driven changes in absorption properties and chemical composition. These results illuminate aging mechanisms and chemical and physical properties of organic aerosols in order to improve atmospheric modeling and the understanding of atmospheric chemical reactions. However, the high chemical complexity and low atmospheric abundance presents a difficult analytical challenge. Milligrams, or more, of material may be needed for speciated spectroscopic analysis.6 This study used a suite of advanced analytical techniques, including a novel combination of action spectroscopy and mass spectrometry that provides more structural information on organic mixtures than mass spectrometry alone. This study also used tunable light from a free electron laser, infrared and UV/Vis absorption, and computational chemistry to characterize molecules in α-pinene SOA. In addition, complex organic mixtures are also found in particulate matter that has deposited onto Earth’s surface. The preliminary results of dew analysis, including a foundation method of analysis for future study, gives the first look at organic material deposited into dew water on natural surfaces. This offers insight into atmospheric organic deposition to better understand chemical transport, air quality, and carbon cycling in the atmosphere.

Naturally occurring humic substances are a combination of decayed plant and soil materials that have been incorporated into a complex matrix with other organic substrates. These acidic humic substances account for a portion of the organic matter found in soil and in the soluble organic portion of fresh water. These humic acids, which are polar and straw-colored, are derived from soil humus and terrestrial and aquatic plants. Considerable attention has been given to these naturally occurring humic materials since the chlorination of these acids in our drinking water results in the formation of trihalomethanes and other chloro-organic compounds. Many of these chlorinated compounds have been determined by the standard Ames Salmonela test to be mutagenic. Despite extensive research concerning humic materials, their structure, and the environmental impact of the derived chlorinated organics are still not fully understood. This research involved an extensive analytical study on a local water source, Forge Pond, which is located in Granby, Massachusetts. The pond water was collected, chlorinated, and analyzed by gas chromatography with electron capture detection to determine the levels of chloro-organics formed when the pH, chlorine dose, and reaction time were varied. It was determined that these variables are critical in the formation of chlorinated organic products. Water was also collected from this pond and the humic material extracted by adsorption and concentration on XAD-8 resin. The thermal properties of the humic materials was studied by Thermal Gravimetric Analysis, and Pyrolysis/Gas Chromatography-Mass Spectrometry was used for chemical characterization. In general, humic acid showed prominent signals related to polysaccharides and phenolic derivatives whereas fulvic acid showed more polysaccharides, and less phenolic signals. A commercial humic acid showed analytical composition mainly related to benzene derivatives.

Newly developed flow field-flow fractionation-inductively coupled plasma mass spectrometry (FlFFF-ICP-MS) has been explored for its capability of size-based elemental speciation. Information obtained from this combination technique includes size and molecular weight distributions, diffusion coefficient, polydispersity, and molecular conformation. Various biological, environmental, and industrial samples are examined to illustrate the versatility of FlFFF-ICP-MS. For biological applications complexation of metals (Co, Cr, Fe, La, Th, and U) with three important proteins (albumin, ferritin, and transferrin) is examined. Size characterization of elements (Al, Cu, Pb, and Zn) in food macromolecules also is investigated. For environmental applications elemental size characterization of Al, Cu, Pb and Zn in humic acids is examined. Physical parameters such as diffusion coefficient and hydrodynamic diameter are determined. Furthermore, FlFFF is employed to study the aggregation of humic acid in the presence of alkaline earth ions (Ca, Sr, and Ba). An equivalent sphere density index (DESI) is proposed and used to trace the conformational arrangement of humic macromolecules. In addition, the FlFFF-ICP-MS is used for elemental size characterization of river and estuarine sediment core samples and aquatic colloids. To demonstrate the scope of the FlFFF-ICP-MS technique with industrial materials, size characterization of Al, Fe, Pb, Si, Ti, and Zr in various chemical mechanical polishing slurries is examined. Particle size information, including size distribution, minimum and maximum particle sizes, average and mean diameters, polydispersity, and breadth of distribution are obtained. Owing to the similarity of FlFFF and a membrane filtration technique, a preliminary investigation of applying a FlFFF channel as an on-channel matrix removal and analyte preconcentration before ICP-MS detection is carried out. Various analyte elements are approximately 50-fold preconcentrated and matrix-removed from 5,000 mg l−1 Ca and Na salt solutions. Frit outlet preconcentration after FlFFF size separation also is examined. With a frit outlet, a standard cross flow nebulizer does not maintain the added benefit from the FlFFF frit outlet. Therefore, use of micronebulizer is necessary for ICP-MS detection and is evaluated in this study.

A mass spectrometry-based method was developed for studying hemoglobin assembly/dissociation. The dynamics of bovine hemoglobin assembly were investigated by monitoring monomers/oligomers equilibria in solution with electrospray ionization mass spectrometry and circular dichroism spectroscopy. The mass spectral data confirm that bovine hemoglobin dissociation involves a step where heme is first lost from the β-chain of the α*β*-dimer to form a heme-deficient dimeric species or semi-hemoglobin dimer (α*β*). The experimental data provide strong evidence that binding of a partially unstructured apo-β-chain to a tightly folded holo-α-chain to form the semi-hemoglobin dimer is the initial step of hemoglobin assembly. Such binding locks the β-chain in a highly ordered conformation, which allows for an efficient heme acquisition. This step is followed by the docking of the two hemoglobin dimers to form a tetrameric form of the protein. Also, investigation of the individual apo- and heme-reconstituted globin chains show that although apo-α- and apo-β-chains are very flexible, dynamic, and have similar protein structures (the globin fold), reconstituted α-chains are monomeric and exhibit conformational structures very similar to holo-α-chains in the complex Hb equilibrium mixture. Reconstituted β-chains oligomerize to form the tetrameric homo-β-globin species HbH found in alpha thalassemic disorder. This suggests that dynamics play an important, perhaps the most important, role in the hemoglobin assembly process. We hypothesize that the intrinsic protein disorder exhibited by the bovine hemoglobin β-chains and the asymmetry of globin interaction reported in this work developed due to evolutionary pressure to provide a vital safeguard that may inhibit random oligomerization and aggregation in the crowded environment of the red blood cell, thus directing the assembly process along the correct pathway. The data support this hypothesis as hemoglobins analyzed from all organisms that evolved after the emergence of separate α- and β-chains (bovine, porcine, human, and modern fish hemoglobins) exhibit the expected asymmetry in the roles played by their globin chains in assembly. In contrast, hemoglobin from the mollusk Scapharca, which parallels the emergence of separate α- and β-chains does not exhibit asymmetry. In the analysis of the modern fish hemoglobin from Gadus morhua, the Atlantic cod, it was noticed that the measured molecular weights for the α- and β-chains did not correspond to masses calculated from their published sequences. Using mass spectrometry-based methods 65% sequence coverage was achieved, and a number of mutations were identified in both globin chains. A feasibility study for the use of mass spectrometry to study the interaction between hemoglobin and its scavenger protein haptoglobin is also presented.