Biocidal and antibiofilm activities of arginine-based surfactants against Candida isolates.

Amino-acid-based surfactants are a group of compounds that resemble natural amphiphiles and thus are expected to have a low impact on the environment, owing to either the mode of surfactant production or its means of disposal. Within this context, arginine-based tensioactives have gained particular interest, since their cationic nature-in combination with their amphiphilic character-enables them to act as broad-spectrum biocides. This capability is based mainly on their interactive affinity for the microbial envelope that alters the latter's structure and ultimately its function.

Interaction of cationic surfactants with DPPC membranes: effect of a novel N-benzoylated arginine-based compound.

Cationic amino acid-based surfactants are known to interact with the lipid bilayer of microorganism resulting in cell death through a disruption of the membrane topology. To elucidate the interaction of a cationic surfactant synthesized in our lab, investigations involving N-benzoyl-arginine decyl amide (Bz-Arg-NHC), and model membranes composed by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were done. Bz-Arg-NHCwas able to penetrate into DPPC monolayers up to a critical pressure of 59.

Temporal dynamics of access to amodal representations of category-level conceptual information.

Categories describe semantic divisions between classes of objects and category-based models are widely used for investigation of the conceptual system. One critical issue in this endeavour is the isolation of conceptual from perceptual contributions to category-differences. An unambiguous way to address this confound is combining multiple input-modalities.

Cationic surfactants as antifungal agents.

Fungi-in being responsible for causing diseases in animals and humans as well as environmental contaminations in health and storage facilities-represent a serious concern to health security. Surfactants are a group of chemical compounds used in a broad spectrum of applications. The recently considered potential employment of cationic surfactants as antifungal or fungistatic agents has become a prominent issue in the development of antifungal strategies, especially if such surface-active agents can be synthesized in an eco-friendly manner.

Volume expansion of erythrocytes is not the only mechanism responsible for the protection by arginine-based surfactants against hypotonic hemolysis.

A novel arginine-based cationic surfactant N-benzoyl-arginine dodecylamide (Bz-Arg-NHC) was synthesized in our laboratory. In this paper we study the interaction of Bz-Arg-NHC with sheep and human red blood cells (SRBC and HRBC respectively) due to their different membrane physicochemical/biophysical properties. SRBC demonstrated to be slightly more resistant than HRBC to the hemolytic effect of the surfactant, being the micellar structure responsible for the hemolytic effect in both cases.

Object individuation and compensation in healthy aging.

Theories on neural compensation suggest that aged participants overactivate the brain areas involved in a task to compensate for the age-related decline. In this electrophysiological study, we investigated the temporal locus of neural overactivation in aging during multiple target processing. We measured performance and three event-related brain potential responses (N1, N2pc, and contralateral delay activity) in young and old adults, while they enumerated a variable number (1-4) of targets presented in an easy (distractor absent) or difficult (distractor present) condition.

Electrophysiological Correlates of Subitizing in Healthy Aging.

To understand the nature of age-related changes in enumeration abilities we measured two ERP responses -N2pc and CDA, associated respectively to attentive individuation and VWM- and posterior alpha band (8-15 Hz) event-related desynchronization (ERD), traditionally linked to enhanced target processing. Two groups of old and young participants enumerated a variable number (1-6) of targets presented among distractors. Older participants were less accurate in enumerating targets.

Biocatalytic synthesis, antimicrobial properties and toxicity studies of arginine derivative surfactants.

Two novel arginine-based cationic surfactants were synthesized using as biocatalyst papain, an endopeptidase from Carica papaya latex, adsorbed onto polyamide. The classical substrate N (α)-benzoyl-arginine ethyl ester hydrochloride for the determination of cysteine and serine proteases activity was used as the arginine donor, whereas decyl- and dodecylamine were used as nucleophiles for the condensation reaction. Yields higher than 90 and 80 % were achieved for the synthesis of N (α)-benzoyl-arginine decyl amide (Bz-Arg-NHC10) and N (α)-benzoyl-arginine dodecyl amide (Bz-Arg-NHC12), respectively.

Attentional processing of multiple targets and distractors.

We assessed the functioning of attention when multiple relevant objects are intermingled with multiple distractors, measuring two electrophysiological subcomponents of the N2pc that have been associated, respectively, with target selection and distractor suppression: the target negativity (Nt) and the distractor positivity (Pd). To this aim, we orthogonally manipulated the number of targets and distractors in an enumeration task. The Nt was modulated by target, but not distractor numerosity, suggesting that an increase in target numerosity leads to an increase in attentional resources needed to form individual representations of the targets.