Biogeochemical and hydrologic synergy control mercury fate in an arid land river-reservoir system.

Reservoirs in arid landscapes provide critical water storage and hydroelectric power but influence the transport and biogeochemical cycling of mercury (Hg). Improved management of reservoirs to mitigate the supply and uptake of bioavailable methylmercury (MeHg) in aquatic food webs will benefit from a mechanistic understanding of inorganic divalent Hg (Hg(II)) and MeHg fate within and downstream of reservoirs. Here, we quantified Hg(II), MeHg, and other pertinent biogeochemical constituents in water (filtered and associated with particles) at high temporal resolution from 2016-2020.

Mass spectrometry-based multi-attribute method in protein therapeutics product quality monitoring and quality control.

The multi-attribute method (MAM), a liquid chromatography-mass spectrometry (LC-MS)-based peptide mapping method, has gained increased interest and applications in the biopharmaceutical industry. MAM can, in one method, provide targeted quantitation of multiple site-specific product quality attributes, as well as new peak detection. In this review, we focus on the scientific and regulatory considerations of using MAM in product quality attribute monitoring and quality control (QC) of therapeutic proteins.

Remobilization of legacy arsenic from sediment in a large subarctic waterbody impacted by gold mining.

Arsenic contamination from mining poses an environmental challenge due to the mobility of this redox-sensitive element. This study evaluated arsenic mobility in sediments of Yellowknife Bay (Canada), a large subarctic water body impacted by gold mining during the 20th century. Short-term measurements of arsenic flux from sediment, arsenic profiling of the water column and sediment porewater, and mass balance modelling were conducted to assess the importance of sediment as an arsenic source.

Challenges and Strategies for a Thorough Characterization of Antibody Acidic Charge Variants.

Heterogeneity of therapeutic Monoclonal antibody (mAb) drugs are due to protein variants generated during the manufacturing process. These protein variants can be critical quality attributes (CQAs) depending on their potential impact on drug safety and/or efficacy. To identify CQAs and ensure the drug product qualities, a thorough characterization is required but challenging due to the complex structure of biotherapeutics.

Experimental evidence for recovery of mercury-contaminated fish populations.

Anthropogenic releases of mercury (Hg) are a human health issue because the potent toxicant methylmercury (MeHg), formed primarily by microbial methylation of inorganic Hg in aquatic ecosystems, bioaccumulates to high concentrations in fish consumed by humans. Predicting the efficacy of Hg pollution controls on fish MeHg concentrations is complex because many factors influence the production and bioaccumulation of MeHg. Here we conducted a 15-year whole-ecosystem, single-factor experiment to determine the magnitude and timing of reductions in fish MeHg concentrations following reductions in Hg additions to a boreal lake and its watershed.

Conformer-Specific Photolysis of Pyruvic Acid and the Effect of Water.

The conformer-specific reactivity of gas-phase pyruvic acid following the S(nπ*) ← S excitation at λ = 350 nm (290-380 nm) and the effect of water are investigated for the two lowest energy conformers. Conformer-specific gas-phase pyruvic acid photolysis rate constants and their respective populations are measured by monitoring their distinct vibrational OH-stretching frequencies. The geometry, relative energies, fundamental vibrational frequencies, and electronic transitions of the pyruvic acid conformers and their monohydrated complexes are calculated with density functional theory and ab initio methods.

A 2D LC-MS/MS Strategy for Reliable Detection of 10-ppm Level Residual Host Cell Proteins in Therapeutic Antibodies.

Methodologies employing LC-MS/MS have been increasingly used for characterization and identification of residual host cell proteins (HCPs) in biopharmaceutical products to ensure their consistent product quality and safety for patients. To improve the sensitivity and reliability for HCP detection, we developed a high pH-low pH two-dimensional reversed phase LC-MS/MS approach in conjunction with offline fraction concatenation. Proof-of -concept was established using a model in which seven proteins spanning a size range of 29-78 kDa are spiked into a purified antibody product to simulate the presence of low-level HCPs.

Atmospheric Simulation Chamber Studies of the Gas-Phase Photolysis of Pyruvic Acid.

Pyruvic acid is an atmospherically abundant α-keto-acid that degrades efficiently from the troposphere via gas-phase photolysis. To explore conditions relevant to the environment, 2-12 ppm pyruvic acid is irradiated by a solar simulator in the environmental simulation chamber, CESAM. The combination of the long path length available in the chamber and its low surface area to volume ratio allows us to quantitatively examine the quantum yield and photochemical products of pyruvic acid.

Multiphase Photochemistry of Pyruvic Acid under Atmospheric Conditions.

Aerosol and molecular processing in the atmosphere occurs in a complex and variable environment consisting of multiple phases and interfacial regions. To explore the effects of such conditions on the reactivity of chemical systems, we employ an environmental simulation chamber to investigate the multiphase photolysis of pyruvic acid, which photoreacts in the troposphere in aqueous particles and in the gas phase. Upon irradiation of nebulized pyruvic acid, acetic acid and carbon dioxide are rapidly generated, which is consistent with previous literature on the bulk phase photolysis reactions.

Gas-Phase Photolysis of Pyruvic Acid: The Effect of Pressure on Reaction Rates and Products.

In this work, we investigate the impact of pressure and oxygen on the kinetics of and products from the gas-phase photolysis of pyruvic acid. The results reveal a decrease in the photolysis quantum yield as pressure of air or nitrogen is increased, a trend not yet documented in the literature. A Stern-Volmer analysis demonstrates this effect is due to deactivation of the singlet state of pyruvic acid when the photolysis is performed in nitrogen, and from quenching of both the singlet and triplet state in air.

Determination of critical quality attributes for monoclonal antibodies using quality by design principles.

Quality by design (QbD) is a global regulatory initiative with the goal of enhancing pharmaceutical development through the proactive design of pharmaceutical manufacturing process and controls to consistently deliver the intended performance of the product. The principles of pharmaceutical development relevant to QbD are described in the ICH guidance documents (ICHQ8-11). An integrated set of risk assessments and their related elements developed at Roche/Genentech were designed to provide an overview of product and process knowledge for the production of a recombinant monoclonal antibody.

Establishing a control system using QbD principles.

Quality by design (QbD) is a global regulatory initiative with the goal of enhancing pharmaceutical development through the proactive design of pharmaceutical manufacturing process and controls to consistently deliver the intended performance of the product. The principles of pharmaceutical development relevant to QbD are described in the ICH guidance documents (ICHQ8-11). An integrated set of risk assessments and their related elements developed at Roche/Genentech were designed to provide an overview of product and process knowledge for the production of a recombinant monoclonal antibody.

Evaluation of Heavy-Chain C-Terminal Deletion on Product Quality and Pharmacokinetics of Monoclonal Antibodies.

Due to their potential influence on stability, pharmacokinetics, and product consistency, antibody charge variants have attracted considerable attention in the biotechnology industry. Subtle to significant differences in the level of charge variants and new charge variants under various cell culture conditions are often observed during routine manufacturing or process changes and pose a challenge when demonstrating product comparability. To explore potential solutions to control charge heterogeneity, monoclonal antibodies (mAbs) with native, wild-type C-termini, and mutants with C-terminal deletions of either lysine or lysine and glycine were constructed, expressed, purified, and characterized in vitro and in vivo.

A sensitive mutation screening method supporting cell line development for biotherapeutics.

Random genetic mutations, which can occur during cell line development, can lead to sequence variants that comprise pharmaceutical product quality generated by recombinant technology. Mutation screening can minimize the probability of selecting clones harboring sequence variants. Here we report a polymerase chain reaction (PCR)-based mutation screening approach using high-resolution melting (HRM) analysis combined with a mutation enrichment step using limiting dilution to detect low-level mutations at 0.

Photochemical kinetics of pyruvic acid in aqueous solution.

Pyruvic acid in the atmosphere is found in both the gas and aqueous phases, and its behavior gives insight into that of other α-keto acids. Photolysis is a significant degradation pathway for this molecule in the environment, and in aqueous solution the major photoproducts are higher-molecular-weight compounds that may contribute to secondary organic aerosol mass. The kinetics of the aqueous-phase photolysis of pyruvic acid under aerobic and anaerobic conditions was investigated in order to calculate the first-order rate constant, Jaq, in solution.

A screening model analysis of mercury sources, fate and bioaccumulation in the Gulf of Mexico.

A mass balance model of mercury (Hg) cycling and bioaccumulation was applied to the Gulf of Mexico (Gulf), coupled with outputs from hydrodynamic and atmospheric Hg deposition models. The dominant overall source of Hg to the Gulf is the Atlantic Ocean. Gulf waters do not mix fully however, resulting in predicted spatial differences in the relative importance of external Hg sources to Hg levels in water, sediments and biota.

Mercury in the Gulf of Mexico: sources to receptors.

Gulf of Mexico (Gulf) fisheries account for 41% of the U.S. marine recreational fish catch and 16% of the nation's marine commercial fish landings.

Engineering upper hinge improves stability and effector function of a human IgG1.

Upper hinge is vulnerable to radical attacks that result in breakage of the heavy-light chain linkage and cleavage of the hinge of an IgG1. To further explore mechanisms responsible for the radical induced hinge degradation, nine mutants were designed to determine the roles that the upper hinge Asp and His play in the radical reactions. The observation that none of these substitutions could inhibit the breakage of the heavy-light chain linkage suggests that the breakage may result from electron transfer from Cys(231) directly to the heavy-light chain linkage upon radical attacks, and implies a pathway separate from His(229)-mediated hinge cleavage.

Charge variants in IgG1: Isolation, characterization, in vitro binding properties and pharmacokinetics in rats.

Antibody charge variants have gained considerable attention in the biotechnology industry due to their potential influence on stability and biological activity. Subtle differences in the relative proportions of charge variants are often observed during routine biomanufacture or process changes and pose a challenge to demonstrating product comparability. To gain further insights into the impact on biological activity and pharmacokinetics (PK) of monoclonal antibody (mAb) charge heterogeneity, we isolated the major charge forms of a recombinant humanized IgG1 and compared their in vitro properties and in vivo PK.

Characterization of oligosaccharides in recombinant tissue plasminogen activator produced in Chinese hamster ovary cells: two decades of analytical technology development.

Recombinant tissue plasminogen activator (rt-PA) is a well-characterized glycoprotein with a great deal of published information on its structure, post-translational modifications, and O- and N-glycosylation. Most of the characterization was accomplished in the late 1980s. During the past 2 decades, however, mass spectrometry has made a quantum leap forward offering new capabilities in soft electrospray ionization, speed, resolution, and accuracy of mass measurements.

Recovery of mercury-contaminated fisheries.

In this paper, we synthesize available information on the links between changes in ecosystem loading of inorganic mercury (Hg) and levels of methylmercury (MeHg) in fish. Although it is widely hypothesized that increased Hg load to aquatic ecosystems leads to increases in MeHg in fish, there is limited quantitative data to test this hypothesis. Here we examine the available evidence from a range of sources: studies of ecosystems contaminated by industrial discharges, observations of fish MeHg responses to changes in atmospheric load, studies over space and environmental gradients, and experimental manipulations.