Abstract: Methods and reagents to obtaining a sample enriched in peptides comprising the third complementarity-determining region of the heavy chain (CDRH3) of immunoglobulins, such as IgGs, are described. These methods are based on the use of targeted protease digestion of immunoglobulins and affinity purification of CDRH3 peptides using specific antibodies. Such methods and reagents are useful for analyzing the immunoglobulin repertoire.

Abstract: A passive-phase-detection photothermal spectroscopy (PTS) system and methods are provided for gas measurements. The PTS system includes a pump laser source, a probe laser source, the pump and probe laser beams simultaneously propagating through an optical waveguide having a target gas specimen. Moreover, the PTS system can be based on a heterodyne detection scheme and includes a combiner configured to align light input from a local oscillator with the probe laser beam output from the optical waveguide to output to a photodetector that is configured to generate beat notes. A demodulation module is configured to detect and measure a photothermal signal based on the beat notes received from the photodetector for gas measurements. The PTS system can also be based on a core-cladding-mode interference detection scheme and generates the core mode and cladding mode simultaneously for the probe laser in the waveguide.