Phenylalanine Photoinduced Fluorescence and Characterization of the Photoproducts by LC-MS

Stability of Protein Pharmaceuticals: Recent Advances

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

Silver Cluster Interactions with Tyrosine: Towards Amino Acid Detection

Tyrosine (Tyr) is involved in the synthesis of neurotransmitters, catecholamines, thyroid hormones, etc. Multiple pathologies are associated with impaired Tyr metabolism. Silver nanoclusters (Ag NCs) can be applied for colorimetric, fluorescent, and surface-enhanced Raman spectroscopy (SERS) detection of Tyr. However, one should understand the theoretical basics of interactions between Tyr and Ag NCs. Thereby, we calculated the binding energy (Eb) between Tyr and Agnq (n = 1-8; q = 0-2) NCs using the density functional theory (DFT) to find the most stable complexes. Since Ag NCs are synthesized on Tyr in an aqueous solution at pH 12.5, we studied Tyr-1, semiquinone (SemiQ-1), and Tyr-2. Ag32+ and Ag5+ had the highest Eb. The absorption spectrum of Tyr-2 significantly red-shifts with the attachment of Ag32+, which is prospective for colorimetric Tyr detection. Ag32+ interacts with all functional groups of SemiQ-1 (phenolate, amino group, and carboxylate), which makes detection of Tyr possible due to band emergence at 1324 cm-1 in the vibrational spectrum. The ground state charge transfer between Ag and carboxylate determines the band emergence at 1661 cm-1 in the Raman spectrum of the SemiQ-1-Ag32+ complex. Thus, the prospects of Tyr detection using silver nanoclusters were demonstrated.

Photo-Oxidation of Therapeutic Protein Formulations: From Radical Formation to Analytical Techniques

UV and ambient light-induced modifications and related degradation of therapeutic proteins are observed during manufacturing and storage. Therefore, to ensure product quality, protein formulations need to be analyzed with respect to photo-degradation processes and eventually protected from light exposure. This task usually demands the application and combination of various analytical methods. This review addresses analytical aspects of investigating photo-oxidation products and related mediators such as reactive oxygen species generated via UV and ambient light with well-established and novel techniques.

Determination of the Total Content of Arsenic, Antimony, Selenium and Mercury in Chinese Herbal Food by Chemical Vapor Generation-Four-Channel Non-dispersive Atomic Fluorescence Spectrometry

Food security is related to safe and nutritious food which meets people's dietary needs and food preferences for an active and healthy life. A simple and feasible method was proposed for the simultaneous analysis of trace arsenic (As), antimony (Sb), selenium (Se) and mercury (Hg) in Chinese herbal food by chemical vapor generation coupled non-dispersive atomic fluorescence spectrometry (CVG-NDAFS) in this paper. The operating parameters, such as observation height, carrier and shield gas flow rate, were optimized. The detection limits were obtained under optimal conditions, which were 0.051, 0.034, 0.050 and 0.0058 ng mL^-1, respectively for As, Sb, Se and Hg. The relative standard deviations were 0.42%, 0.74%, 0.97% and 1.0% (n = 7), respectively (10 ng mL^-1of As, Sb, Se and 1 ng ml^-1of Hg). The proposed method is verified to simultaneously determine As, Sb, Se and Hg for Chinese herbal food.