Determination of individual chain length and chain-length distribution of polyphosphates in microalgae by 31P-DOSY-NMR

Abstract

Due to its ecological and biotechnological relevance, polyphosphate in microalgae is currently the focus of intense research. Numerous biological functions are performed by or dependent on polyphosphate, and they depend, among other factors, on its chain length. Chain length determination is important for understanding polyphosphate metabolism and for maximizing intracellular polyphosphate abundance per unit weight of biomass. 31 P-DOSY NMR virtually separates various polyphosphate polymers in a mixture based on different translational diffusion coefficients. The diffusion coefficient of a polyphosphate molecule correlates with its molecular weight, enabling determination of individual chain lengths. Moreover, the polydispersity index can also be uniquely determined by DOSY as a measure of the overall chain-length distribution of polyphosphates. By contrast, conventional 31 P NMR is only able to estimate the average chain length of the entire polyphosphate pool. Therefore, DOSY provides the opportunity to deepen our insight into polyphosphate metabolism and dynamics in algal biomass.

Methods for the Analysis of Polyphosphate in the Life Sciences

“…31 P NMR quantitatively measures the polyP structure (linear, cyclic, or branched polyP), the total polyP, the average polyP chain length, and the polyP chain length distribution (as a sum parameter) with high specificity. One study has been published recently where the chain length of individual polyPs in a sample was determined . The measurement can be done without ( in vivo ) or with prior extraction of the polyP.…”

“…A value of 1 would mean a uniform chain length. 31 P DOSY NMR appears to be a facile approach and a promising technique for the estimation of the polydispersity index and even the chain length of individual polyPs within a sample …”

Periphyton Phosphorus Uptake in Response to Dynamic Concentrations in Streams: Assimilation and Changes to Intracellular Speciation

“…Length of polyphosphate chains, represented here by the ratio of polyphosphate end groups to polyphosphate middle groups, , was also associated with SRP pulse concentration both 1 and 10 days after applying the SRP pulse treatment (Figure E). Polyphosphate chain length ratios ranged from 1.05 to 1.83 and 0.42 to 1.34 along the SRP pulse concentration gradient for samples collected 1 day and 10 days after, respectively.…”

Extraction processes reduce polyphosphate ion migration, dispersion and diffusion as detected with gel electrophoresis and 31P DOSY NMR

“…A polydispersity index (PDI), which indicates the broadness of a molecular weight distribution, can be estimated by DOSY NMR diffusion data using the following equation [34, 35]: $$\begin{equation}PDI\; = {\left( {\frac{{\langle {D_w}\rangle }}{{\langle {D_n}\rangle }}} \right)^{ - {d_f}}}\;\end{equation}$$where D w is the polyP mid‐chain diffusion coefficient, and D n is the end‐chain (terminal) phosphate unit diffusion coefficient. The constant d f has a value between 5/3 and 3 and represents the molecule's fractal dimension [36].…”

“…A polydispersity index (PDI), which indicates the broadness of a molecular weight distribution, can be estimated by DOSY NMR diffusion data using the following equation [34,35]:…”