The ionization state of D37 in E. coli porin OmpF and the nature of conductance fluctuations in D37 mutants.

Understanding the flow of ions through E. coli porin outer membrane protein F (OmpF) requires knowledge of the charge state of all titratable residues located along the permeation pathway. Earlier theoretical studies proved successful in the calculation of the pK values of most residues.

A biological porin engineered into a molecular, nanofluidic diode.

We changed the nonrectifying biological porin OmpF into a nanofluidic diode. To that end, we engineered a pore that possesses two spatially separated selectivity filters of opposite charge where either cations or anions accumulate. The observed current inhibition under applied reverse bias voltage reflects, we believe, the creation of a zone depleted of charge carriers, in a sense very similar to what happens at the np junction of a semiconductor device.

Ca2+ selectivity of a chemically modified OmpF with reduced pore volume.

We studied an E. coli OmpF mutant (LECE) containing both an EEEE-like locus, typical of Ca(2+) channels, and an accessible and reactive cysteine. After chemical modification with the cysteine-specific, negatively charged (-1e) reagents MTSES or glutathione, this LECE mutant was tested for Ca(2+) versus alkali metal selectivity.

Conductance and selectivity fluctuations in D127 mutants of the bacterial porin OmpF.

A recent molecular dynamics study questioned the protonation state and physiological role of aspartate 127 (D127) of E. coli porin OmpF. To address that question we isolated two OmpF mutants with D127 either neutralized (D127N) or replaced by a positively charged lysine (D127K).

Channel activity of OmpF monitored in nano-BLMs.

Free-standing lipid bilayer membranes can be formed on small apertures (60 nm diameter) on highly ordered porous alumina substrates. The formation process of the membranes on a 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol submonolayer was followed by impedance spectroscopy. After lipid bilayers had thinned, the reconstitution and ionic conducting properties of the outer membrane protein OmpF of E.

Chemical modification of the bacterial porin OmpF: gain of selectivity by volume reduction.

OmpF is an essentially nonselective porin isolated from the outer membrane of Escherichia coli. Here we report on the manipulation of the ion selectivity of OmpF by chemical modification with MTS reagents (MTSET, MTSEA, and MTSES) and the (rather bulky) tripeptide glutathione, all cysteine specific. When recorded in a gradient of 0.

Basic principles, applications in oncology and improved selectivity of photodynamic therapy.

Photodynamic therapy (PDT) is a promising approach for the treatment of superficially localized tumors. This review starts with a summary of the basic principles of PDT, in which the current practice, the photochemical mechanisms, cellular and subcellular targets, as well as the most prominent photosensitizers are discussed. Next, the clinical results obtained with PDT for the treatment of a variety of tumor types are outlined.

Comparison of aluminium (III) phthalocyanine tetrasulfonate- and meta-tetrahydroxyphenylchlorin-monoclonal antibody conjugates for their efficacy in photodynamic therapy in vitro.

A challenge in photodynamic therapy (PDT) is to improve the tumour selectivity of the photosensitizers by using monoclonal antibodies (MAbs). With this aim, we developed MAb-conjugates with the hydrophobic photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC) and with the hydrophilic sensitizer aluminium (III) phthalocyanine tetrasulfonate (AlPcS(4)). The capacity of these photoimmunoconjugates for selective targeting of squamous cell carcinoma (SCC) in vivo was demonstrated previously in SCC-bearing nude mice.