Search results for " quaternary"

The Middle-Late Quaternary littoral deposits of Western Sicily coastal belt (southern Italy): sedimentology and geomorphology

A multidisciplinary study has been carried out on the littoral deposits located along the western Sicily coastal belt, central Mediterranean region, with the aim of unravelling their origin and evolution through analysis of their lithology, texture, sedimentary structures, and geomorphological features. The deposits crop out between the towns of Trapani and Marsala and are distributed from the present-day coastline up to 120 m above sea level, forming four major discrete ridges in the landscape, each of separated by topographic depressions with flat or slightly concave upwards surfaces. The ridges ranging between 5 to 30 m in height, display a NNE-SSW trend almost parallel to the present-da…

Eustatic and oceanographic control on sedimentary evolution of middle-late Quaternary shelf margin-to-upper slope deposits on the Egadi Islands offsh…

2016

During the past decades a number of sequence stratigraphy studies illustrated how, during Quaternary, interaction between sea level changes and sediment supply controlled the depositional evolution along continental margins, giving a cyclic signature to the sedimentary infilling. However, as both deposition and erosion are processes ultimately controlled by balance between environmental energy and sedimentary influx, also the oceanographic regime takes part in controlling the sedimentary growth along the continental margin. This is exactly what occurs on physiographic settings as islands offshore areas, where bottom currents can be very energetic. In the western Sicily offshore, southwards …

A Multidisciplinary approach to define the Plio-Quaternary tectonics in the Termini Imerese Mts. (Northern central Sicily)

2012

Resistance to disinfection of a polymicrobial association contaminating the surface of elastomeric dental impressions.

2009

The aim of this study was to evaluate the ability to resist disinfection of a polymicrobial association contaminating the surface of dental impressions obtained with two different elastomers: a polyether (Impregum) and an addition-polymerized silicone (Elite). Impressions were contaminated with a mixture of three biofilm-forming microorganisms (Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans) and disinfected immediately after contamination, or after microbial layers were allowed to develop during a six-hour storage. Two commercial disinfectants were tested: MD 520 containing 0.5% glutaraldehyde and Sterigum Powder without glutaraldehyde. Residual contamination was recover…

Role of SH-Groups and S-S Bridges in the Main Subunit (1/12 Molecule) of Spirographis Spallanzanii Chlorocruorin

1986

In all species of annelids described, the extracellular hemoglobins show (by electron microscopy) the same quaternary structure constituted by twelve identical subunits. The fine structure of the 1/12 subunit is not well resolved and several models have been proposed for it (2).

High-resolution crystal structure of an avidin-related protein: insight into high-affinity biotin binding and protein stability.

2004

The chicken avidin gene belongs to an extended gene family encoding seven avidin-related genes (AVRs), of which only avidin is expressed in the chicken. The sequences of AVR4 and AVR5 are identical and the common protein (AVR4) has been expressed both in insect and bacterial systems. The recombinant proteins are similarly hyperthermostable and bind biotin with similarly high affinities. AVR4 was crystallized in the apo and biotin-complexed forms and their structures were determined at high resolution. Its tertiary and quaternary structures are very similar to those of avidin and streptavidin. Its biotin-binding site shows only a few alterations compared with those of avidin and streptavidin…

Recombinant NeutraLite Avidin: a non-glycosylated, acidic mutant of chicken avidin that exhibits high affinity for biotin and low non-specific bindin…

2000

AbstractA recombinant non-glycosylated and acidic form of avidin was designed and expressed in soluble form in baculovirus-infected insect cells. The mutations were based on the same principles that guided the design of the chemically and enzymatically modified avidin derivative, known as NeutraLite Avidin. In this novel recombinant avidin derivative, five out of the eight arginine residues were replaced with neutral amino acids, and two of the lysine residues were replaced by glutamic acid. In addition, the carbohydrate-bearing asparagine-17 residue was altered to an isoleucine, according to the known sequences of avidin-related genes. The resultant mutant protein, termed recombinant Neutr…

Dimer-tetramer transition between solution and crystalline states of streptavidin and avidin mutants.

2003

ABSTRACT The biotin-binding tetrameric proteins, streptavidin from Streptomyces avidinii and chicken egg white avidin, are excellent models for the study of subunit-subunit interactions of a multimeric protein. Efforts are thus being made to prepare mutated forms of streptavidin and avidin, which would form monomers or dimers, in order to examine their effect on quaternary structure and assembly. In the present communication, we compared the crystal structures of binding site W→K mutations in streptavidin and avidin. In solution, both mutant proteins are known to form dimers, but upon crystallization, both formed tetramers with the same parameters as the native proteins. All of the intersub…

Thermal Aggregation of Bovine Serum Albumin in Trehalose and Sucrose Aqueous Solutions

2012

We report results of static and dynamic light scattering measurements performed on bovine serum albumin (BSA) in saccharide (trehalose and sucrose) solutions. Our aim is to study the effects of the two disaccharides on the first steps of thermal aggregation of BSA in aqueous solutions at two protein concentrations (1 and 30 mg/mL) at increasing sugar/water ratio. Results show that sugars modify early stages of aggregation mainly by perturbing the thermodynamic behavior of the solvent (i.e., general solvent effects) without involving direct, specific sugar-protein interactions. This agrees with current hypotheses on sugar action in protein solutions. (1-3) The linear correlation detected bet…

Aβ Oligomers and Fibrillar Aggregates Induce Different Apoptotic Pathways in LAN5 Neuroblastoma Cell Cultures

2009

Fibril deposit formation of amyloid beta-protein (Abeta) in the brain is a hallmark of Alzheimer's disease (AD). Increasing evidence suggests that toxicity is linked to diffusible Abeta oligomers, which have been found in soluble brain extracts of AD patients, rather than to insoluble fibers. Here we report a study of the toxicity of two distinct forms of recombinant Abeta small oligomers and fibrillar aggregates to simulate the action of diffusible Abeta oligomers and amyloid plaques on neuronal cells. Different techniques, including dynamic light scattering, fluorescence, and scanning electron microscopy, have been used to characterize the two forms of Abeta. Under similar conditions and …