Chromatographic separation by RPLC-ESI-MS of all hydroxyproline isomers for the characterization of collagens from different sources

During collagen biosynthesis, proline is post-translationally converted to hydroxyproline by specific enzymes. This amino acid, unique to collagen, plays a crucial role in stabilizing the collagen triple helix structure and could serve as an important biomarker for collagen content and quality analysis. Hydroxyproline has four isomers, depending on whether proline is hydroxylated at position 4 or 3 and on whether the cis- or trans- conformation is formed. Moreover, as extensive hydrolysis of collagen is required for its amino acid analysis, epimerization may also occur, although to a lesser extent, giving a total of eight possible isomers. The aim of the present study was to develop a reversed-phase high-performance liquid chromatography-UV-mass spectrometry (RPLC-UV-MS) method for the separation and quantification of all eight hydroxyproline isomers. After the chiral derivatization of the hydroxyproline isomers with Nα-(2,4-dinitro-5-fluorophenyl)-L-valinamide (L-FDVA), to enable their UV detection, the derivatized diastereoisomers were separated by testing different C18 column technologies and morphologies and optimizing operative conditions such as the mobile phase composition (solvent, additives), elution mode, flow rate and temperature. Baseline resolution of all eight isomers was achieved on a HALO® ES-C18 reversed-phase column (150×1.5 mm, 2.7 μm, 160 Å) using isocratic elution and MS-compatible mobile phase. The optimized method was validated for the quantification of hydroxyproline isomers and then applied to different collagen hydrolysates to gain insight and a deeper understanding of hydroxyproline abundances in different species (human, chicken) and sources (native, recombinant).

Development of a rapid, efficient, and reusable magnetic bead-based immunocapture system for recombinant human procollagen type II isolation from yeast fermentation broth

Recombinant collagen production, especially using yeasts as expression systems, could represent a promising alternative over traditional extractive methods from animal sources, offering controllable, scalable, and high-quality products. Monitoring the efficiency and efficacy of procollagen/collagen expression, especially in the initial fermentation phases, can be difficult and time consuming, as biological matrices necessitate purification and commonly used analytical methods are only partially informative. We propose a straightforward, efficient, and reusable immunocapture system able to specifically isolate human procollagen type II from fermentation broths and to release it in few experimental steps. A recovered sample allows for a detailed characterization providing information on structural identity and integrity, which can strongly support the monitoring of fermentation processes. The immunocapture system relies on the use of protein A-coated magnetic beads which have been functionalized and cross-linked with a human anti-procollagen II antibody (average immobilization yield of 97.7%) to create a stable and reusable support for the specific procollagen fishing. We set up the binding and release conditions ensuring specific and reproducible binding with a synthetic procollagen antigen. The absence of non-specific interaction with the support and binding specificity was demonstrated, and the latter was also confirmed by a peptide mapping epitope study in reversed-phase liquid chromatography high-resolution mass spectrometry (RP-LC-HRMS). The bio-activated support proved to be reusable and stable over 21 days from the initial use. Finally, the system was successfully tested on a raw yeast fermentation sample to provide a proof of concept of the applicability within recombinant collagen production.