Structural analysis of HS(CD(2))(12)(O-CH(2)-CH(2))(6)OCH(3) monolayers on gold by means of polarization modulation infrared reflection absorption spectroscopy. progress of the reaction with bromine

Effects of Piptoporus betulinus Ethanolic Extract on the Proliferation and Viability of Melanoma Cells and Models of Their Cell Membranes

Piptoporus betulinus is a fungus known for its medicinal properties. It possesses antimicrobial, anti-inflammatory, and anti-cancer activity. In this study, several tests were performed to evaluate the cytotoxic effect of the ethanolic extract of Piptoporus betulinus on two melanoma human cell lines, WM115 primary and A375 metastatic cell lines, as well as Hs27 human skin fibroblasts. The extract proved to affect cancer cells in a dose-dependent manner, and at the same time showed a low cytotoxicity towards the normal cells. The total phenolic content (TPC) was determined spectrophotometrically by the Folin-Ciocalteu method (F-C), and the potential antioxidant activity was measured by ferric-reducing antioxidant power (FRAP) assay. One of the active compounds in the extract is betulin. It was isolated and then its cytotoxic activity was compared to the results obtained from the Piptoporus betulinus extract. To further understand the mechanism of action of the extract's anticancer activity, tests on model cell membranes were conducted. A model membrane of a melanoma cell was designed and consisted of 1,2-dimyristoyl-sn-glycero-3-phosphocholine, disialoganglioside-GD_1a and cholesterol: DMPC:GD_1a:chol (5:2:3 mole ratio). Changes in a Langmuir monolayer were observed and described based on Π-A_mol isotherm and compressibility modulus changes. LB lipid bilayers were deposited on a hydrophilic gold substrate and analyzed by IR and X-ray photoelectron spectroscopy. Our study provides new data on the effect of Piptoporus betulinus extract on melanoma cells and its impact on the model of melanoma plasma membranes.

The Ca2+ response of a smart forisome protein is dependent on polymerization

Forisomes are giant self-assembling mechanoproteins that undergo reversible structural changes in response to Ca²⁺ and various other stimuli. Artificial forisomes assembled from the monomer MtSEO-F1 can be used as smart biomaterials, but the molecular basis of their functionality is not understood. To determine the role of protein polymerization in forisome activity, we tested the Ca²⁺ association of MtSEO-F1 dimers (the basic polymerization unit) by circular dichroism spectroscopy and microscale thermophoresis. We found that soluble MtSEO-F1 dimers neither associate with Ca²⁺ nor undergo structural changes. However, polarization modulation infrared reflection absorption spectroscopy revealed that aggregated MtSEO-F1 dimers and fully-assembled forisomes associate with Ca²⁺ , allowing the hydration of poorly-hydrated protein areas. A change in the signal profile of complete forisomes indicated that Ca²⁺ interacts with negatively-charged regions in the protein complexes that only become available during aggregation. We conclude that aggregation is required to establish the Ca²⁺ response of forisome polymers.

Structural changes in the model of the outer cell membrane of Gram-negative bacteria interacting with melittin: an in situ spectroelectrochemical study

The cell membrane of Gram-negative bacteria interacting with an antimicrobial peptide presents a complex supramolecular assembly. Fabrication of models of bacterial cell membranes remains a large experimental challenge. Langmuir-Blodgett and Langmuir-Schaefer (LS-LB) transfer makes possible the deposition of multicomponent asymmetric lipid bilayers onto a gold surface. Two lipids: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and di[3-deoxy-D-manno-octulosonyl]-lipid A (KLA) were used to deposit a model of the outer membrane of Gram-negative bacteria on the Au(111) substrate. The use of gold as the solid substrate enables control of the membrane potential. Molecular scale changes in the model membrane exposed to physiological electric fields and interacting with melittin antimicrobial peptide are discussed in this paper. The interaction of the outer membrane with melittin leads to an increase in the membrane capacitance and permeability to ions and water. The stability of the outer membrane with bound melittin decreases at positive membrane potentials. In situ polarization modulation infrared reflection absorption spectroscopy is used to investigate membrane potential-dependent changes in the structure of the outer membrane interacting with melittin. The hydration of the ester carbonyl groups is not affected by the interaction with melittin. However, the orientation and hydrogen bond network with the carboxylate groups in KLA changes drastically after POPE-KLA bilayer interacts with melittin. We propose that the positively charged groups in the amino acids present at the C-terminus of the peptide interact directly with the polar head group of KLA. Simultaneously, the packing order in hydrocarbon chains in the membrane with bound melittin increases. A hydrophobic match between the chains in the lipids and the peptide, which spans the membrane, seems to be responsible for the ordering of the hydrocarbon chains region of the bilayer. The N-terminus enters into the hydrophobic region of the membrane and forms a channel to the hydrophilic head groups in POPE.

Microfabrication of patterns of adherent marine bacterium Phaeobacter inhibens using soft lithography and scanning probe lithography

Two lithographic approaches have been explored for the microfabrication of cellular patterns based on the attachment of marine bacterium Phaeobacter inhibens strain T5. Strain T5 produces a new antibiotic that makes this bacterium potentially interesting for the pharmaceutical market and as a probiotic organism in aquacultures and in controlling biofouling. The microcontact printing (microCP) method is based on the micropatterning of self-assembled monolayers (SAMs) terminated with adhesive end groups such as CH(3) and COOH and nonadhesive groups (e.g., short oligomers of ethylene glycol (OEG)) to form micropatterned substrates for the adhesion of strain T5. The scanning probe lithographic method is based on the surface modification of OEG SAM by using a microelectrode, the probe of a scanning electrochemical microscope (SECM). Oxidizing agents (e.g., Br(2)) were electrogenerated in situ at the microelectrodes from Br(-) in aqueous solution to remove OEG SAMs locally, which allows the subsequent adsorption of bacteria. Various micropatterns of bacteria could be formed in situ on the substrate without a prefabricated template. The fabricated cellular patterns may be applied to a variety of marine biological studies that require the analysis of biofilm formation, cell-cell and cell-surface interactions, and cell-based biosensors and bioelectronics.