Membrane-Dependent Binding and Entry Mechanism of Dopamine into Its Receptor

Synaptic neurotransmission has recently been proposed to function via either a membrane-independent or a membrane-dependent mechanism, depending on the neurotransmitter type. In the membrane-dependent mechanism, amphipathic neurotransmitters first partition to the lipid headgroup region and then diffuse along the membrane plane to their membrane-buried receptors. However, to date, this mechanism has not been demonstrated for any neurotransmitter-receptor complex. Here, we combined isothermal calorimetry measurements with a diverse set of molecular dynamics simulation methods to investigate the partitioning of an amphipathic neurotransmitter (dopamine) and the mechanism of its entry into the ligand-binding site. Our results show that the binding of dopamine to its receptor is consistent with the membrane-dependent binding and entry mechanism. Both experimental and simulation results showed that dopamine favors binding to lipid membranes especially in the headgroup region. Moreover, our simulations revealed a ligand-entry pathway from the membrane to the binding site. This pathway passes through a lateral gate between transmembrane alpha-helices 5 and 6 on the membrane-facing side of the protein. All in all, our results demonstrate that dopamine binds to its receptor by a membrane-dependent mechanism, and this is complemented by the more traditional binding mechanism directly through the aqueous phase. The results suggest that the membrane-dependent mechanism is common in other synaptic receptors, too

Structural dynamics and physicochemical properties of pDNA/DODAB:MO lipoplexes : effect of pH and anionic lipids in inverted non-lamellar phases versus lamellar phases

Dioctadecyldimethylammoniumbromide (DODAB):Monoolein (MO) lipoplexes have mainly been studied within the range of high molar ratios of DODAB, with noticeable transfection efficiencies in the Human Embryonic Kidney (HEK, a.k.a. 293T) cell line. In thiswork,we intend to study the effect of highMOcontent on the structure and physicochemical properties of pDNA/DODAB:MOlipoplexes to achieve some correlationwith their transfection efficiency. Static/Dynamic Light Scattering and Cryo-TEM imaging were used to characterize the size/ morphology of DNA/DODAB:MO lipoplexes at different DODAB:MO contents (2:1, 1:1, 1:2) and charge ratios (CRs) (+/−). Nile Red fluorescence emission was performed to detect changes in microviscosity, hydration and polarity of DNA/DODAB:MO systems. Lipoplexes stability at physiological pH values and in the presence of anionic lipids was evaluated by Förster Resonance Energy Transfer (FRET). Physicochemical/structural data were complemented with transfection studies in HEK cells using the β-galactosidase reporter gene activity assay. This work reports the coexistence of multilamellar and non-lamellar inverted phases in MO-richer lipoplexes (DODAB:MO 1:2 and 1:4), leading to transfection efficiencies comparable to those of multilamellar (DODAB-richer) lipoplexes, but at higher charge ratios [CR (+/−) = 6.0] and without dose-effect response. These results may be related to the structural changes of lipoplexes promoted by high MO content.FEDER (037291) through POFC — COMPETEFundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/46968/2009 (PhD grant), PEst-C/BIA/UI4050/2011(CBMA), PEst-C/FIS/UI0607/2011 (CFUM)

Curcumin parametrization in the CHARMM force field

The atomic charges and the equilibrium values of the geometrical parameters for the neutral enol form of curcumin and its monoanion derived according to the methodology developed for the CGenFF force field.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Synteza i właściwości antybakteryjne czwartorzędowej amoniowej pochodnej polietylenoiminy

The quaternary derivative of branched polyethylenimine (bPEI-met) was synthesized and its antibacterial activity against Gram-positive bacterium (Staphylococcus aureus) and Gram-negative bacterium (Escherichia coli) was studied. The values of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of bPEI-met against mentioned bacteria were determined. These indicated that bPEI-met could be considered as an effective alternative to antibiotics for the treatment of selected bacterial strains. The results obtained can be useful in search for drugs allowing treatment of antibiotic resistant bacterial strains.Zsyntetyzowano czwartorzędową amoniową pochodną rozgałęzionej polietylenoiminy (bPEI-met) i badano jej działanie antybakteryjne przeciwko bakteriom Gram-dodatnim na przykładzie gronkowca złocistego (Staphylococcus aureus) i Gram-ujemnym na przykładzie pałeczki okrężnicy (Escherichia coli). Wyznaczono wartości minimalnego stężenia hamującego (MIC) i minimalnego stężenia bakteriobójczego (MBC) bPEI-met w stosunku do obu wymienionych szczepów bakterii. Wyniki tych badań sugerują, że bPEI-met może być rozważana jako alternatywa dla antybiotyków w zwalczaniu wybranych szczepów bakterii, szczególnie tych, które charakteryzują się antybiotykoopornością

Zmiany fizykochemicznych właściwości gleby lekkiej użyźnionej osadem sciekowym i wermikompostem osadowym

An influence of varied (1, 2.5, 5, 10, 20) doses of dry mass of the fermented sludge sewage and sedimentary vermicompost, used in the light soil, on physico-chemical properties of the soil. It was found out that the increasing doses of the tested unconventional fertilizers have an essential impact on reaction, sorbtive properties and contents of biogenous components. The influence of the fermented sediments was little more advantageous than the vermicompost's in given above matters The impact of the vermicompost was beneficial in forming a ratio of C (carbon) :N (nitrogen), what is related to a different rate of mineralization of organic matter

PEGylated Liposomes as Carriers of Hydrophobic Porphyrins

Sterically stabilized liposomes (SSLs) (PEGylated liposomes) are applied as e ff ective drug delivery vehicles. Under- standing the interactions between hydrophobic compounds and PEGylated membranes is therefore important to determine the e ff ectiveness of PEGylated liposomes for delivery of drugs or other bioactive substances. In this study, we have combined fl uorescence quenching analysis (FQA) experiments and all-atom molecular dynamics (MD) simulations to study the e ff ect of membrane PEGylation on the location and orientation of 5,10,15,20-tetrakis(4- hydroxyphenyl)porphyrin (p-THPP) that has been used in our study as a model hydrophobic compound. First, we consider the properties of p-THPP in the presence of di ff erent fl uid phosphatidylcholine bilayers that we use as model systems for protein-free cell membranes. Next, we studied the interaction between PEGylated membranes and p-THPP. Our MD simulation results indicated that the arrangement of p-THPP within zwitterionic membranes is dependent on their free volume, and p-THPP solubilized in PEGylated liposomes is localized in two preferred positions: deep within the membrane (close to the center of the bilayer) and in the outer PEG corona (p-THPP molecules being wrapped with the polymer chains). Fluorescence quenching methods con fi rmed the results of atomistic MD simulations and showed two populations of p-THPP molecules as in MD simulations. Our results provide both an explanation for the experimental observation that PEGylation improves the drug-loading e ffi ciency of membranes and also a more detailed molecular-level description of the interactions between porphyrins and lipid membranes