Data From: Shedding light on cobalamin photodegradation in the ocean

Cobalamin, vitamin B12, is an important micronutrient that has been investigated for decades in the marine context because it is required for phytoplankton growth. The biologically active forms (Me-B12, Ado-B12) and the synthetic form (CN-B12) quickly convert to OH-B12 after light exposure in various aqueous solutions, but puzzlingly have been frequently reported to dominate dissolved cobalamin pools in the sunlit ocean. Here we document photodegradation timescales for these cobalamin forms in natural seawater using targeted mass spectrometry, providing quantitative evidence that OH-B12 is expected to be the dominant dissolved form in irradiated seawater. Then, through high resolution mass spectrometry, we identify four photodegradation products of OH-B12 which represent potential building blocks microbes could salvage and remodel to satisfy cellular cobalamin requirements. Taken together, these results clarify the impact of light on marine cobalamin dynamics, laying a foundation for a ..., Analytical cobalamin standards
Cobalamin standards CN-B12 (≥ 98%, Fisher BioReagents), Me-B12 (≥ 97%, Sigma-Aldrich), Ado-B12 (≥ 97%, Sigma-Aldrich) and OH-B12 (≥ 95%, Supelco) were obtained and primary stock solutions were prepared by dissolving 1 mg of each compound in 1 mL of Optima LC-MS grade water and stored at –80°C in the dark until use.
Seawater collection
We collected seawater from CTD rosette bottles into amber HDPE bottles while protecting from light, then filtered (0.2 µm pore-size nylon filters) while protected from light and stored at -20°C in acid-washed, milli-Q water rinsed, and sample-rinsed amber HDPE bottles until processing. Surface seawater (< 5 m) samples were collected from Lat: 43.1822; Lon: -62.0983 (Station HL05) on May 26th, 2022, and Lat: 41.4100; Lon: -60.6772 (Station HL12) on May 23rd, 2022, in the Northwest Atlantic.
Photodegradation experiments  
Thirty-minute experiment: we added 8 pM of Me- and Ado-, and 5 pM of CN-B12 and OH-B12 into 15 mL of sea..., ,