Différentes approches pour la modélisation de l’électroporation des membranes cellulaires

Cell electroporation is a complex phenomenon, which consists in the emergence of defects in cell membranes subjected to electric pulses. Since the end of the 90’s biophysical models have been developed to explain and predict the conditions for cell electroporation. However the recent biological data, in particular those dealing with the influence of the repetition rate of the pulses challenge these biophysical models. In this chapter we introduce different biophysical models of electropore formation and we discuss their mathematical basis and their advantages and disadvantages. We also present the phenomenological modeling, which consists in designing the model on an empirical basis thanks to the experience. The aim of the chapter is to introduce the reader to different ways of modeling cell membrane electroporation, and to provide some possible directions to obtain a more reliable theory of electroporation in accordance with the experiments and with a justified theoretical basis.Le but de ce rapport est de présenter les différentes approches biophysiques et phénoménologiques développées pour d´écrire l’électroperméabilisation de la membrane cellulaire. Nous repartons des modèles simples de circuits électriques équivalents, et celui de Schwan décrivant la membrane comme un condensateur mis en parallèle avec une résistance. Ensuite nous présentons les principes de la théorie de l’électroporation développée dans les années 90’ à partir des énergies libres des membranes, et qui a fait l’objet depuis de quelques modifications. Enfin nous présentons les approches phénoménologiques récentes qui permettent de comparer les données expérimentales et les simulations numériques. L’objectif est présenter les avantages et les désavantages de chaque approche afin d’ouvrir de possibles directions de recherches pour obtenir une théorie de l’électroporation plus en accord avec les observations, tout en se fondant sur une base théorique solide

Direct transesterification of microalgae after Pulsed Electric Field ( PEF ) treatment

Background Lipid extraction is a major bottleneck for the commercialization of microalgae due to energy costs involved during solvent recycling. Direct transesterification offers the possibility to bypass the extraction step by immediately converting the lipids to fatty acids methyl esters (FAMEs). In this study, the efficiency of direct transesterification after pulsed electric field (PEF) was evaluated. Freshly harvested Auxenochlorella protothecoides (A. protothecoides), cultivated either autotrophically or mixotrophically, was subjected to PEF. Two treatment energies were tested, 0.25 MJ/kgdw and 1.5 MJ/kgdw and results were compared with conventional two-step transesterification. Results For autotrophically grown A. protothecoides, the percentage of the total FAMEs recovered from untreated biomass and microalgae treated with 0.25 MJ/kgdw was 30% for both cases while for 1.5 MJ/kgdw it was 65%. A 24-h incubation step between PEF-treatment and direct transesterification significantly improved the results. Untreated biomass remained stable with 30% of FAMEs, while with both treatment energies a 97% FAME recovery was achieved. However, for mixotrophic A. protothecoides the process was not as effective. Approximately 30% of FAMEs were recovered for all three conditions immediately after PEF with only a marginal increase after incubation. The reason for this different behavior of the two cultivation modes is unknown and under investigation. Conclusions Overall, the synergy between PEF and direct transesterification was proven to have potential, in particular for autotrophic microalgae. Its implementation and further optimization in a biorefinery therefore merits further attention

Direct transesterification of microalgae after Pulsed Electric Field ( PEF ) treatment

Background Lipid extraction is a major bottleneck for the commercialization of microalgae due to energy costs involved during solvent recycling. Direct transesterification offers the possibility to bypass the extraction step by immediately converting the lipids to fatty acids methyl esters (FAMEs). In this study, the efficiency of direct transesterification after pulsed electric field (PEF) was evaluated. Freshly harvested Auxenochlorella protothecoides (A. protothecoides), cultivated either autotrophically or mixotrophically, was subjected to PEF. Two treatment energies were tested, 0.25 MJ/kgdw and 1.5 MJ/kgdw and results were compared with conventional two-step transesterification. Results For autotrophically grown A. protothecoides, the percentage of the total FAMEs recovered from untreated biomass and microalgae treated with 0.25 MJ/kgdw was 30% for both cases while for 1.5 MJ/kgdw it was 65%. A 24-h incubation step between PEF-treatment and direct transesterification significantly improved the results. Untreated biomass remained stable with 30% of FAMEs, while with both treatment energies a 97% FAME recovery was achieved. However, for mixotrophic A. protothecoides the process was not as effective. Approximately 30% of FAMEs were recovered for all three conditions immediately after PEF with only a marginal increase after incubation. The reason for this different behavior of the two cultivation modes is unknown and under investigation. Conclusions Overall, the synergy between PEF and direct transesterification was proven to have potential, in particular for autotrophic microalgae. Its implementation and further optimization in a biorefinery therefore merits further attention

Parathyroid hormone receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The parathyroid hormone receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Parathyroid Hormone Receptors [47]) are family B G protein-coupled receptors. The parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor (PTH1 receptor) is activated by precursor-derived peptides: PTH (84 amino acids), and PTHrP (141 amino-acids) and related peptides (PTH-(1-34), PTHrP-(1-36)). The parathyroid hormone 2 receptor (PTH2 receptor) is activated by the precursor-derived peptide TIP39 (39 amino acids). [125I]PTH may be used to label both PTH1 and PTH2 receptors

Parathyroid hormone receptors in GtoPdb v.2021.3

The parathyroid hormone receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Parathyroid Hormone Receptors [49]) are class B G protein-coupled receptors. The parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor (PTH1 receptor) is activated by precursor-derived peptides: PTH (84 amino acids), and PTHrP (141 amino-acids) and related peptides (PTH-(1-34), PTHrP-(1-36)). The parathyroid hormone 2 receptor (PTH2 receptor) is activated by the precursor-derived peptide TIP39 (39 amino acids). [125I]PTH may be used to label both PTH1 and PTH2 receptors. The structure of a long-active PTH analogue (LA-PTH, an hybrid of PTH-(1-13) and PTHrP-(14-36)) bound to the PTH1 receptor-Gs complex has been resolved by cryo-electron microscopy [147]. Another structure of a PTH-(1-34) analog bound to a thermostabilized inactive PTH1 receptor has been obtained with X-ray crytallography [34]

Parathyroid hormone receptors in GtoPdb v.2023.1

The parathyroid hormone receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Parathyroid Hormone Receptors [50]) are class B G protein-coupled receptors. The parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor (PTH1 receptor) is activated by precursor-derived peptides: PTH (84 amino acids), and PTHrP (141 amino-acids) and related peptides (PTH-(1-34), PTHrP-(1-36)). The parathyroid hormone 2 receptor (PTH2 receptor) is activated by the precursor-derived peptide TIP39 (39 amino acids). [125I]PTH may be used to label both PTH1 and PTH2 receptors. The structure of a long-active PTH analogue (LA-PTH, an hybrid of PTH-(1-13) and PTHrP-(14-36)) bound to the PTH1 receptor-Gs complex has been resolved by cryo-electron microscopy [148]. Another structure of a PTH-(1-34) analog bound to a thermostabilized inactive PTH1 receptor has been obtained with X-ray crytallography [35]