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Highlights • The wide size spectrum (3 µm–5 mm) of Arctic particles and plankton was analysed. • The spatial variability was caused by hydro-dynamic forcing in the Fram Strait. • The bathymetry, water currents and ice influenced particles and plankton structure. • The rich biological hotspot was recognized in the northern shallow part. Abstract Changes within marine pelagic fields in the Arctic affect global biogeochemical cycles. The size structure and distribution of particles and plankton (P&P) were studied in the main northward passage of Atlantic water to the Arctic region, which is affected in various ways by climate change. The wide size spectrum of P&P (3 µm–5 mm) was assessed by combining measurements from two complementary optical counters, a Laser In-Situ Scattering and Transmissometry (LISST) instrument and a Laser Optical Plankton Counter (LOPC). The measurements were performed in the upper 100 m layer at 55 stations in summer in 2013. The P&P were attributed to various functional groups – particles, phytoplankton, marine snow, and zooplankton – to test their spatial coupling with hydrodynamic forcing. Although our study confirms that the Fram Strait is a region of strong biophysical contrasts, the expected coastal-offshore gradient has not been distinguished clearly. Three mechanisms could explain P&P patches: particle flocculation due to contact with fresh waters from ice and fjords, enhanced production due to coastal upwelling as well as widening the range of warm surface water advection northwards. Particularly rich biological hot spots were recognised in the northern, shallow parts of the west Spitsbergen shelf, and near the marginal ice edges, confirming that these areas are highly vulnerable to marine predators. Moreover, combining optical measurements from two size-specific optical counters contributes greatly to reducing the substantial knowledge gap regarding wide size structure and distribution of thus far neglected seawater components, such as non-living particles and marine snow aggregates, occurring in this vulnerable Arctic region. [ABSTRACT FROM AUTHOR]

Antimicrobial and cell-penetrating peptides have inspired developments of abiotic membrane-active polymers that can coat, penetrate, or break lipid bilayers in model systems. Application to cell cultures is more recent, but remarkable bioactivities are already reported. Synthetic polymer chains were tailored to achieve (i) high biocide efficiencies, and selectivity for bacteria (Gram-positive/Gram-negative or bacterial/mammalian membranes), (ii) stable and mild encapsulation of viable isolated cells to escape immune systems, (iii) pH-, temperature-, or light-triggered interaction with cells. This review illustrates these recent achievements highlighting the use of abiotic polymers, and compares the major structural determinants that control efficiency of polymers and peptides. Charge density, sp. of cationic and guanidinium side groups, and hydrophobicity (including polarity of stimuli-responsive moieties) guide the design of new copolymers for the handling of cell membranes. While polycationic chains are generally used as biocidal or hemolytic agents, anionic amphiphilic polymers, including Amphipols, are particularly prone to mild permeabilization and/or intracell delivery. [ABSTRACT FROM AUTHOR]

Glycine-9 and leucine-10 of substance P (SP) are critical for (NK)-1 receptor recognition and agonist activity. Proψ(Z)-CH=CH(CH3)-CONH)Leu (or Met) and Proψ((E)-CH=CH(CH3)-CONH)Leu (or Met) have been introduced in the sequence of SP, in order to restrict the conformational flexibility of the C-terminal tripeptide, Gly-Leu-Met-NH2, of SP. Proψ((Z)-CH=C(CH2CH(CH3)2)-CONH)Met-NH2, with an isobutyl substituent to mimic the Leu side-chain, was also incorporated in place of the C-terminal tripeptide. The substituted-SP analogs were tested for their affinity to human NK-1 receptor specific binding sites (NK-1M and NK-1m) and their potency to stimulate adenylate cyclase and phospholipase C in Chinese Hamster ovary (CHO) cells transfected with the human NK-1 receptor. The most potent SP analogs [Pro9 ψ((Z)CH=C(CH3)CONH)Leu10]SP and [Pro9 ψ ((E)CH=C(CH3)CONH)Leu10]SP, are about 100-fold less potent than SP on both binding sites and second messenger pathways. These vinylogous(Z)- or(E)-CH=C(CH3)- or(Z)-CH=C(CH2CH(CH3)2) moieties hamper the correct positioning of the C-terminal tripeptide of SP within both the NK-1M- and NK-1m-specific binding sites. The origin of these lower potencies is related either to an incorrect peptidic backbone conformation and/or an unfavorable receptor interaction of the methyl or isobutyl group. [ABSTRACT FROM AUTHOR]

This study deals with the effect of annealing temperature of Polyvinylidene Fluoride quenched from melt into ice-water on the dielectric behavior. Measurements were carried out in the temperature range 25°C to 130°C and in the frequency range 1 kHz to 10 MHz. It was found that the dielectric permittivity and dielectric strength decreases with increasing annealing temperature. This is a result of morphological changes including defects creation, recrystallization and additional crystallization at expense of the amorphous phases. [ABSTRACT FROM AUTHOR]

The need to replace natural amino acids in peptides with nonproteinogenic counterparts to obtain new medicinal agents has stimulated a great deal of innovation on synthetic methods. Here, we report the incorporation of non-natural silylated amino acids in substance P (SP), the binding affinity for the two hNK-1 binding sites and, the potency to stimulate phospholipase C (PLC) and adenylate cyclase of the resulting peptide. We also assess the improvement of their stability towards enzyme degradation. Altogether, we found that replacing glycine with silaproline (Sip) in position 9 of SP leads to a potent analogue exhibiting an increased resistance to angiotensin-converting enzyme hydrolysis. [ABSTRACT FROM AUTHOR]

Numerous photoaffinity studies of the NK-1 receptor have been carried out with peptide agonist analogues of substance P (SP). However, no information is available with regard to the domain interaction of peptide antagonists within this receptor. We describe herein the photoaffinity labelling of the SP receptor with a peptide antagonist analogue, Bapa0[(pBzl)Phe8,DPro9,MePhe10,Trp(CHO)11]SP. Photolabelling, enzymatic or chemical cleavage of the covalent complex, purification via streptavidin-coated beads and matrix-assisted laser desorption/ionization time of flight mass spectrometry analysis led us to show that the methyl of Met174 side chain, within the receptor’s second extracellular loop, is covalently linked to the antagonist photoreactive at position 8. [Copyright &y& Elsevier]

Abstract: The initial goal of this study was to analyze, using photolabeling, the interactions between Substance P and its tachykinin NK-1 receptor. Therefore, the photoreactive amino acid para-benzoyl-phenylalanine (pBzl)Phe was incorporated into the Substance P sequence from position 4 to 11 leading to Bapa[sup 0][(pBzl)Phe[sup x]]SP analogs. Biotinyl sulfone-5-aminopentanoic acid (Bapa) was introduced in order to purify the covalent complex. These photoreactive SP analogs were first assayed for their affinity for the two binding sites associated with the NK-1 receptor, as well as for their potency in activating the phospholipase C and adenylate cyclase pathways. All analogs photoreactive from position 4 to 11 have moderate to high affinity for the two NK-1 receptor-binding sites, except for the analog modified at position 7. This affinity could be correlated to their potency to activate the phospholipase C and adenylate cyclase pathways, except for the analog photoreactive at position 11. Bapa[sup 0][(pBzl)Phe[sup 11]]SP was found to be an agonist in the phospholipase C pathway and an antagonist in the adenylate cyclase pathway, other analogs modified at position 11 were therefore analyzed. Among these, Bapa[sup 0][Pro[sup 9], (pBzl)Hcy(O[sub 2])[sup 11]]SP is a partial agonist, whereas Bapa[sup 0][Hcy(ethylaminodansyl)[sup 11]]SP is a full agonist in the phospholipase C pathway, the two analogs being antagonist in the adenylate cyclase pathway. These results show that analogs of SP can be simultaneously agonist at one binding site and antagonist at the other binding site associated with the NK-1 receptor. [ABSTRACT FROM AUTHOR]

Penetratin is a cell penetrating peptide (CPP) that can enter cells by direct translocation through the plasma membrane. The molecular mechanism of this translocation still remains poorly understood. Here we provide insights on this mechanism by studying the direct translocation of the peptide across model membranes based on Droplet Interface Bilayers (DIBs), which are bilayers at the interface between two adhering aqueous-in-oil droplets. We first showed with symmetric bilayers made of a mix of 1-palmitoyl-2-oleoyl- sn -glycero-3-phospho-(1′- rac -glycerol) (POPG) and 1,2-dioleoyl- sn -glycero-3-phosphocholine (POPC) that the translocation of penetratin required the presence of at least 40% of POPG on both leaflets. Interestingly when replacing POPG with another anionic lipid 1-palmitoyl-2-oleoyl- sn -glycero-3-phospho- l -serine (POPS), translocation was inefficient. To elucidate the lipid partners required at each step of the CPP translocation process, we then investigated the crossing of asymmetric bilayers. We found that POPG on the proximal leaflet and POPS on the distal leaflet allowed penetratin translocation. Translocation was not observed when POPS was on the proximal leaflet and POPG on the distal leaflet or if POPS on the distal leaflet was replaced with POPC. These observations led us to propose a three-step translocation mechanism: (i) peptide recruitment by anionic lipids, (ii) formation of a transient peptide-lipid structure leading to the initiation of translocation which required specifically POPG on the proximal leaflet, (iii) termination of the translocation process favored by a driving force provided by anionic lipids in the distal leaflet. Unlabelled Image • Asymmetric droplet interface bilayers are used to assess penetratin translocation • Penetratin translocation is favored by POPG lipids • POPG is required on the proximal leaflet to initiate translocation • We determine which lipids are necessary for each step of the translocation [ABSTRACT FROM AUTHOR]