R. De Almeida

Basics on growth orders of polymonogenic functions

In this paper, we introduce generalizations of the classical growth order and the growth type of analytic functions in the context of polymonogenic functions. Polymonogenic functions are null-solutions of higher integer order iterates of a generalized higher dimensional Cauchy–Riemann operator. One of the main goals is to prove generalizations of the famous Lindelöf–Pringsheim theorem linking explicitly these growth orders and growth types with the Taylor series coefficients in the context of this function class.

Phospholipid/cholesterol/decanethiol mixtures for direct assembly of immunosensing interfaces

In this work, a simple yet robust method to prepare lipid-based biosensing interfaces on gold using common lipids (a phospholipid and cholesterol) and an alkanethiol is reported. The lipids were carefully chosen to tailor the biophysical properties of the bilayer. The simplicity of the method relies on the incorporation of a small percentage of decanethiol in the lipid vesicles for a direct formation of a thiol-linked supported lipid bilayer, which is advantageous in several respects. It prevents the use of specially synthesized thiolipids and preserves the natural fluidity and dynamics of the lipids. As a consequence the whole arrangement is extremely stable regarding ionic strength changes and solution flow during surface plasmon resonance experiments. Moreover, we show that this interface is very effective on suppressing the nonspecific adsorption of proteins on the surface, and enables the covalent attachment of the recognition antibody. The subsequent detection of specific interaction toward antigen was monitored in real-time by SPR and confirmed by ellipsometric measurements. This lipid-based biosensing platform is versatile and can be adapted to the biorecognition reaction of interest.

Growth Orders of Monogenic Functions in the Ball

In this paper we give some first results on the asymptotic growth behavior of monogenic Taylor series of finite convergence radius. We set up some estimates on their growth orders and discuss basic properties.

m-Cresol affects the lipid bilayer in membrane models and living neurons

m-Cresol is a preservative used in pharmaceutical formulations, including insulin and vaccines, which contain up to 30 millimolar concentrations of this excipient. We studied the effects of m-cresol (from 1:1 to 1:104 dilution relative to the formulations) on membrane model systems containing liquid ordered domains, alone or in an insulin formulation. These studies allowed to understand the effects of this compound on cell membranes when present in pharmaceutical formulations, and to explain its cytotoxic effects. Changes in the intrinsic fluorescence of m-cresol showed a clear interaction with liposomes that depends on their lipid composition. Liposomes labeled with several membrane probes revealed the superficial location of m-cresol, alone and within insulin formulation, with an unusual preference for liquid ordered cholesterol–sphingolipid-enriched domains due to their high membrane dipole potential. Membrane probes detected the effects of m-cresol at a concentration of 1:10000 relative to the original formulations. Atomic force microscopy imaging of ternary supported lipid bilayers allowed the observation that addition of m-cresol affects precisely the ordered raft-like nanodomains, with a fast (5 min) effect at 1:10 dilution that became massive after 1 h. When contained in insulin formulation, similar m-cresol effects were observed. To evaluate the importance of the direct interactions of m-cresol with membrane lipids at the cellular level, membrane leakage was monitored in three neuronal cell lines. m-Cresol was applied during constant superfusion and leak current alterations were followed. The leak conductance in living neurons underwent a dose-dependent increase. The effects reported here are likely to underlie the mechanisms of m-cresol toxicity for cells and tissues at or near the injection site.