Physicochemical properties of mixed micellar aggregates containing CCK peptides and Gd complexes designed as tumor specific contrast agents in MRI

New amphiphilic molecules containing a bioactive peptide or a claw moiety have been prepared in order to obtain mixed micelles as target-specific contrast agents in magnetic resonance imaging. The first molecule, C18H37CONH(AdOO)2-G-CCK8 (C18CCK8), contains a C18 hydrophobic moiety bound to the C-terminal cholecystokinin octapeptide amide (CCK 26-33 or CCK8). The second amphiphilic compound, C18H37CONHLys(DTPAGlu)CONH2 (C18DTPAGlu) or its gadolinium complex, (C18DTPAGlu- (Gd)), contains the same C18 hydrophobic moiety bound, through a lysine residue, to the DTPAGlu chelating agent. The mixed aggregates as well as the pure C18DTPAGlu aggregate, in the presence and absence of Gd, have been fully characterized by surface tension measurements, FT-PGSE-NMR, fluorescence quenching, and small-angle neutron scattering measurements. The structural characterization of the mixed aggregates C18DTPAGlu(Gd)-C18CCK8 indicates a spherical arrangement of the micelles with an external shell of 21 Å and an inner core of 20 Å. Both the DTPAGlu(Gd) complexes and the CCK8 peptides point toward the external surface. The measured values for relaxivity in saline medium at 20 MHz proton Larmor frequency and 25 °C are 18.7 mM-1 s-1. These values show a large enhancement in comparison with the isolated DTPAGlu(Gd) complex

Interaction between Alzheimer's Aβ(25–35) peptide and phospholipid bilayers: The role of cholesterol

AbstractThere is mounting evidence that the lipid matrix of neuronal cell membranes plays an important role in the accumulation of β-amyloid peptides into senile plaques, one of the hallmarks of Alzheimer's disease (AD). With the aim to clarify the molecular basis of the interaction between amyloid peptides and cellular membranes, we investigated the interaction between a cytotoxic fragment of Aβ(1–42), i.e., Aβ(25–35), and phospholipid bilayer membranes. These systems were studied by Electron Paramagnetic Resonance (EPR) spectroscopy, using phospholipids spin-labeled on the acyl chain. The effect of inclusion of charged phospholipids or/and cholesterol in the bilayer composition was considered in relation to the peptide/membrane interaction. The results show that Aβ(25–35) inserts in bilayers formed by the zwitterionic phospholipid dilauroyl phosphatidylcholine (DLPC), positioning between the outer part of the hydrophobic core and the external hydrophilic layer. This process is not significantly influenced by the inclusion of the anionic phospholipid phosphatidylglycerol (DLPG) in the bilayer, indicating the peptide insertion to be driven by hydrophobic rather than electrostatic interactions. Cholesterol plays a fundamental role in regulating the peptide/membrane association, inducing a membrane transition from a fluid-disordered to a fluid-ordered phase. At low cholesterol content, in the fluid-disordered phase, the insertion of the peptide in the membrane causes a displacement of cholesterol towards the more external part of the membrane. The crowding of cholesterol enhances its rigidifying effect on this region of the bilayer. Finally, the cholesterol-rich fluid-ordered membrane looses the ability to include Aβ(25–35)

Enforcing the positive charge of N-termini enhances membrane interaction and antitumor activity of bovine seminal ribonuclease

AbstractBinding to cell membrane, followed by translocation into the cytosol and RNA degradation, is a necessary requirement to convert a ribonuclease into a cytotoxin for malignant tumor cells. In this paper, we investigate the membrane binding attitude of bovine seminal ribonuclease (BS-RNase) and its variant G38K-BS-RNase, bearing an enforced cluster of positive charges at the N-termini surface. By using a combination of biophysical techniques, including CD, SPR and ESR, we find for the two proteins a common, two-step mechanism of interaction with synthetic liposomes, an initial binding to the bilayer surface, driven by electrostatic interactions, followed by a shallow penetration in the lipid core. Protein binding effectively perturbs lipid packing and dynamics. Remarkably, the higher G38K-BS-RNase membrane interacting capability well correlates with its increased cytotoxicity for tumor cells. Overall, these studies shed light on the mechanism of membrane binding and perturbation, proving definitely the importance of electrostatic interactions in the cytotoxic activity of BS-RNase, and provide a rational basis to design proteins with anticancer potential

perspectives and potential applications of ruthenium based nanocarriers for cancer therapy

Perspectives and Potential Applications of Ruthenium-Based Nanocarriers for Cancer Therapy Rita Santamaria*1 , Carlo Irace1, Gerardino D'Errico 2, Daniela Montesarchio2 and Luigi Paduano2 1Department of Pharmacy, University of Napoli "Federico II", via D. Montesano 49, I-80131, Napoli, Italy 2Department of Chemical Sciences, University of Napoli "Federico II", Complesso Universitario di Monte Sant'Angelo, via Cintia 21, I-80126, Napoli, Italy *Corresponding author: Rita Santamaria, Associate Professor, Department of Pharmacy, University of Napoli "Federico II", via D. Montesano 49, I-80131, Napoli, Italy, Fax: 0039081678403, Tel: 0039 081678421, E-Mail: [email protected] Citation: Rita Santamaria, Carlo Irace, Gerardino D'Errico, Daniela Montesarchio, Luigi Paduano (2013) Perspectives and Potential Applications of Ruthenium-Based Nanocarriers for Cancer Therapy. J Pharm Drug Devel 1(2): e201. doi: 10.15744/2348-9782.1.e201 Received Date: September 30, 2013 Accepted Date: October 15, 2013 Published Date: October 23, 2013 Editorial Open Acces

Biophysical Characterization and Membrane Interaction of the Two Fusion Loops of Glycoprotein B from Herpes Simplex Type I Virus

The molecular mechanism of entry of herpesviruses requires a multicomponent fusion system. Cell invasion by Herpes simplex virus (HSV) requires four virally encoded glycoproteins: namely gD, gB and gH/gL. The role of gB has remained elusive until recently when the crystal structure of HSV-1 gB became available and the fusion potential of gB was clearly demonstrated. Although much information on gB structure/function relationship has been gathered in recent years, the elucidation of the nature of the fine interactions between gB fusion loops and the membrane bilayer may help to understand the precise molecular mechanism behind herpesvirus-host cell membrane fusion. Here, we report the first biophysical study on the two fusion peptides of gB, with a particular focus on the effects determined by both peptides on lipid bilayers of various compositions. The two fusion loops constitute a structural subdomain wherein key hydrophobic amino acids form a ridge that is supported on both sides by charged residues. When used together the two fusion loops have the ability to significantly destabilize the target membrane bilayer, notwithstanding their low bilayer penetration when used separately. These data support the model of gB fusion loops insertion into cholesterol enriched membranes

Microstructural characterization of phospholipid membranes and study of their interaction with peptides and proteins

In the present thesis, a wide structural and functional study on biomembranes is presented. The research has been focused on the micro- and mesostructure of phospholipid bilayers and on their interactions with different peptides which are involved in important biological process. Particularly, the role of lipid composition and self-organization in regulating the membrane biophysical properties has been investigated. In particular, the experimental study is aimed to contribute to the analysis of the fine interplay between lipids and proteins/peptides in regulating processes involving biomembranes. The experimental work has been divided in two parts. In the former one, the attention has been focused on the formulation and the contemporary physico-chemical characterization of biomimicking lipid systems, as liposomes and supported lipid bilayers. Different classes of lipids were considered, incluiding zwitterionic and anionic, mono- and bichained, mono-, bi- and polyunsaturated phospholipids. Cholesterol and sphingolipids were also used in order to discriminate the effect of lipid composition in modulating the microstructural properties of lipid bilayers and their mesoscopic organization. In the latter part of the research, the interaction of these lipid systems with peptides deriving from different viral glycoproteins as well as from the A peptide was analyzed. The whole investigation was realized by a combined experimental approach in which many physico-chemical techniques were used in order to obtain a wide description of the systems structure and behavior. In particular, Electron Spin Resonance (ESR) spectroscopy and Neutron Reflectivity (NR) have provided information about the lipid ordering and dynamics in the bilayer, while spectrofluorimetry and circular dichroism (CD) measurements have allowed the direct monitoring of the peptides behavior in the presence of membrane environment. Finally, Dynamic Light Scattering (DLS) and Small Angle Neutron Scattering (SANS) experiments have permitted a mesoscopic analysis of the different lipid supramolecular aggregates

On the segregative tendency of ethoxylated surfactants in nonionic mixed micelles

The aqueous mixtures of two nonionic surfactants, pentaethyleneglycol monohexyl ether (C6E5) and hexyl dimethyl phosphine oxide (C6DMPO), were investigated by the pulsed-gradient stimulated-echo NMR technique. Quite unexpectedly, the results show that the mixture behavior significantly deviates from ideality. Particularly, analysis of the data indicates that, in the mixed aggregates, C6E5 molecules prefer to be surrounded by other C6E5 molecules, forming domains of hydrated ethoxilic chains on the micellar surface. Molecular reasons for the segregative tendency of ethoxylated surfactants and its applicative implications in formulation technology are discussed