54 research outputs found
Spectroscopic approaches to resolving ambiguities of hyper-polarized NMR signals from different reaction cascades
Ambiguities in identifying transient intracellular reaction intermediates are resolved by site-specific isotope labelling, optimised referencing and response to external perturbations.</p
Hyperpolarised Organic Phosphates as NMR Reporters of Compartmental pH
When formed in defined cellular compartments from exogenous hyperpolarised13C substrates, metabolites yield correlations of compartmental pH and catalytic activity.</p
Detecting Elusive Intermediates in Carbohydrate Conversion: A Dynamic Ensemble of Acyclic Glucose-Catalyst Complexes
The role of acyclic carbohydrates
in pathways toward value-added
chemicals has remained poorly characterized due to the low population
of acyclic forms, and due to their instability under reaction conditions.
We conduct steady-state and pre-steady-state measurements by direct
reaction progress monitoring with sensitivity-optimized NMR spectroscopy
in the molybdate-catalyzed epimerization of glucose to mannose. We
detect an exchanging pool of at least 5 acyclic glucose–catalyst
complexes under near-optimum reaction conditions. In the presence
of catalyst, the acyclic glucose population increases within few seconds
prior to reaching a steady state. Exchange between the acyclic intermediates
increases under conditions that favor epimerization. Species accounting
for less than 0.05% of total glucose can be monitored with subsecond
time resolution to allow kinetic analysis of intermediate formation
and catalytic conversion. Epimerization occurs 2–3 orders of
magnitude faster than the binding of acyclic glucose to the catalyst
under near-optimum reaction conditions. The current study brings insight
into the nature of acyclic intermediate-catalyst complexes of very
low population and into experimental strategies for characterizing
very minor intermediates in carbohydrate conversion to value-added
compounds
Kinetic Analysis of Hexose Conversion to Methyl Lactate by Sn Beta: Effects of Substrate Masking and of Water
Strategies to tailor the Sn-Beta-catalysed methyl lactate process are identified by kinetic and mechanistic insights.</p
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