Régulation de l'activité exoprotéolytique bactérienne aux concentrations naturelles en matière organique dissoute dans un marais maritime

Crottereau, C.; Delmas, Daniel

doi:10.1016/s0764-4469(00)88524-8

Cited by 1 publication

(1 citation statement)

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“…The only comparison of TDFPA and chromatographic analysis of DFAA made on a wide set of samples (Delmas et al, 1990) led to a relatively good correlation between these two pools, indicating that variations of TDFPA can mostly be attributed to DFAA. Daumas (1976) stated that amino acids are involved in abiotic (metal complexation) and biotic (excretion, assimilation, enzymatic regulation) processes (Fuhrman, 1987;Jørgensen, 1987;Crottereau and Delmas, 1999). While their main source in seawater is primary production, they account for only a minor fraction of dissolved organic matter (DOM) because of their high turnover rate which makes them an important source of carbon and nitrogen for heterotrophic bacteria (Fuhrman and Bell, 1985), and to a lesser extent for phytoplankton.…”

Section: Introductionmentioning

confidence: 99%

The determination of total dissolved free primary amines in seawater: Critical factors, optimized procedure and artefact correction

Aminot

Kérouel

2006

Marine Chemistry

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The paper reviews the methods described in the literature for the determination of total dissolved free primary amines (TDFPA) by fluorescence. A wide set of reaction conditions can be found, but they rely on few experiments for their validation. Among fluorogenic compounds, o-phthaldialdehyde (OPA) is more sensitive than fluorescamine and was thus examined here. However, the use of mercaptoethanol (ME) in the reaction (as an additional derivatization compound) is able to generate unreliable results, in particular when standardization relies on glycine. We suggest replacing ME with 3-mercaptopropionic acid (MPA) which induces more stable and comparable fluorescence among amine compounds. A systematic study was therefore undertaken to define reagent concentrations and pH effects on the reaction rates for a variety of primary amines with particular focus on amino acids. The reaction rate is increased by increasing OPA concentration and pH, but slowed by excess MPA. Ammonium interference is influenced by several factors, but spectral investigation showed that the choice of conditions can drastically reduce it. The magnitudes of natural and OPA-induced background fluorescence signals have been assessed in various mediums and it is shown that their contribution to the signal amounts to a large fraction, when not most, of the measured fluorescence. A segmented flow method is proposed with a protocol for adequate correction of biases. ABSTRACTThe paper reviews the methods described in the literature for the determination of total dissolved free primary amines (TDFPA) by fluorescence. A wide set of reaction conditions can be found, but they rely on few experiments for their validation. Among fluorogenic compounds, ophthaldialdehyde (OPA) is more sensitive than fluorescamine and was thus examined here. However, the use of mercaptoethanol (ME) in the reaction (as an additional derivatization compound) is able to generate unreliable results, in particular when standardization relies on glycine. We suggest replacing ME with 3-mercaptopropionic acid (MPA) which induces more stable and comparable fluorescence among amine compounds. A systematic study was therefore undertaken to define reagent concentrations and pH effects on the reaction rates for a variety of primary amines with particular focus on amino acids. The reaction rate is increased by increasing OPA concentration and pH, but slowed by excess MPA. Ammonium interference is influenced by several factors, but spectral investigation showed that the choice of conditions can drastically reduce it. The magnitude of natural and OPA-induced background fluorescence signals have been assessed in various mediums and it is shown that their contribution to the signal amounts to a large fraction, when not most, of the measured fluorescence. A segmented flow method is proposed with a protocol for adequate correction of biases.

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