Research Associate / Senior Research Associate – Protein Expression & Analytics

Company: JLSa2
Location: South San Francisco
Posted on: February 7, 2026

Job Description:

JLSa2 is a recently launched seed-stage venture backed company located in South San Francisco focused on developing novel multifunctional protein-drug conjugate therapies to address human metabolic diseases and other non-oncology related diseases. We are seeking a highly motivated Research Associate / Senior Research Associate to support protein expression and characterization efforts in a fast-paced startup environment. This individual will primarily work with mammalian cell expression systems (CHO and HEK293) using transient transfection and will contribute to routine analytical and quality control workflows. The ideal candidate is hands-on, detail-oriented, and comfortable adapting to evolving priorities. Key Responsibilities Perform transient transfections in CHO and HEK293 cells for recombinant protein expression Maintain mammalian cell cultures using aseptic technique, including passaging, expansion, and harvest Operate and maintain cell counters (e.g., Vi-CELL or equivalent) for viability and cell density measurements Execute routine QC and analytical assays, including: SDS-PAGE SEC-HPLC RP-HPLC Accurately document experimental procedures, results, and deviations in lab notebooks or ELN Support troubleshooting of expression, purification, or analytical issues Collaborate closely with scientists across protein purification, bioconjugation and analytical teams Assist with general lab operations as needed (inventory, equipment upkeep, method optimization) Required Qualifications Bachelor’s or Master’s degree in Biology, Biochemistry, Biotechnology, or a related field 1–4 years of hands-on experience in a biotech or academic lab setting Practical experience with: Mammalian cell culture (CHO and/or HEK293) Transient transfection workflows Aseptic technique Familiarity with protein QC techniques such as SDS-PAGE and chromatography-based assays Familiarity with Microsoft Office programs: Excel and PowerPoint Strong organizational skills and attention to detail Ability to work independently while contributing effectively to a team Preferred Qualifications Experience with SEC-HPLC and RP-HPLC method execution or data interpretation Exposure to protein purification workflows (e.g., affinity chromatography) Experience working in a startup or fast-moving research environment Comfort learning new techniques and taking on responsibilities outside a narrowly defined role What We’re Looking For Flexible, adaptable, and malleable mindset—priorities may shift quickly in a startup setting Strong sense of ownership and accountability Willingness to “wear multiple hats” and grow with the company Curiosity and enthusiasm for building processes from the ground up Compensation range $75,000 to $110,000 depending on experience and level.

Keywords: JLSa2, San Jose , Research Associate / Senior Research Associate – Protein Expression & Analytics, Science, Research & Development , South San Francisco, California