Search results for "trap"

The role of plasma lipid transfer proteins in lipoprotein metabolism and atherogenesis.

2008

The plasma lipid transfer proteins promote the exchange of neutral lipids and phospholipids between the plasma lipoproteins. Cholesteryl ester transfer protein (CETP) facilitates the removal of cholesteryl esters from HDL and thus reduces HDL levels, while phospholipid transfer protein (PLTP) promotes the transfer of phospholipids from triglyceride-rich lipoproteins into HDL and increases HDL levels. Studies in transgenic mouse models and in humans with rare genetic deficiencies (CETP) or common genetic variants (CETP and PLTP) highlight the central role of these molecules in regulating HDL levels. Human CETP deficiency is associated with dramatic elevations of HDL cholesterol and apolipopr…

Conditional transgenic mouse models: from the basics to genome-wide sets of knockouts and current studies of tissue regeneration

2008

Many mouse models are currently available, providing avenues to elucidate gene function and to recapitulate specific pathological conditions. To a large extent, successful translation of clinical evidence or analytical data into appropriate mouse models is possible through progress in transgenic or gene-targeting technology. Beginning with a review of standard mouse transgenics and conventional gene targeting, this article will move on to discussing the basics of conditional gene expression: the tetracycline (tet)-off and tet-on systems based on the transactivators tet-controlled transactivator (Tta) and reverse tet-on transactivator (rtTA) that allow downregulation or induction of gene exp…

The human complement C9 gene: structural analysis of the 5′ gene region and genetic polymorphism studies

2001

Summary C9 is the last of the human complement components creating the membrane attack complex. The single chain serum protein is encoded by a gene located on chromosome 5p13 that is composed of 11 exons. With the aid of inverse PCR, the hitherto unknown regions flanking exon 1 and the 3′ part of exon 11 (3′UTR) have been sequenced. A computer-based analysis of the 300-bp region located just upstream of the AUG start codon showed homologies to known DNA modules which affect the transcriptional regulation of certain genes. The most striking of these is a sequence that may substitute the missing TATA box in initiating C9 transcription. In the 3′UTR, three successive polyadenylation signals we…

Murine Cytomegalovirus Major Immediate-Early Enhancer Region Operating as a Genetic Switch in Bidirectional Gene Pair Transcription

2007

ABSTRACT Enhancers are defined as DNA elements that increase transcription when placed in any orientation relative to a promoter. The major immediate-early (MIE) enhancer region of murine cytomegalovirus is flanked by transcription units ie1/3 and ie2 , which are transcribed in opposite directions. We have addressed the fundamental mechanistic question of whether the enhancer synchronizes transcription of the bidirectional gene pair (synchronizer model) or whether it operates as a genetic switch, enhancing transcription of either gene in a stochastic alternation (switch model). Clonal analysis of cytokine-triggered, transcription factor-mediated MIE gene expression from latent viral genomes…

Geologia e Geomorfologia dell'area.

2008

Soil Erosion and Deposition Rate Inside an Artificial Reservoir in Central Italy: Bathymetry versus RUSLE and Morphometry

2022

This study, using different direct and indirect methodologies, evaluated the sedimentation rate in an artificial reservoir in central Italy. This reservoir is regionally representative and was built in the 1960s for hydroelectric purposes; it has experienced a strong decrease in trap efficiency and a loss of over 70% of the stored water volume. Direct measurements of the lake bottom bathymetry, carried out in 2006 and 2015, and 3D reconstructions performed in a GIS environment, made it possible to calculate the volume of filling material and to verify an increasing trend in the sedimentation rate since 2006. The sample reservoir denudation rate was compared with that obtained using the Revi…

Photoinduced dissociation of anionic and electron detachment of dianionic gold clusters by use of a laser pointer

2002

Abstract Size-selected anionic and dianionic gold clusters have been stored in a Penning trap and irradiated with the green light of a laser pointer. As examples of special interest, the systems Au 7 − and Au 29 2− have been chosen. In particular, Au 7 − , a small gold cluster with closed electron shell, is observed to decay into Au 6 − and Au 5 − with a decay pathway branching ratio similar to that of Au 9 + . The dianionic cluster Au 29 2− shows electron detachment upon photoexcitation. This observation is in agreement with independent experiments [Stoermer et al., Int. J. Mass Spectrom. 201 (2001) 63], where Au 29 2− is found to be the smallest dianion produced by neutral monomer evapora…

The influence of the trapping potential on the attachment of a second electron to stored metal cluster and fullerene anions

2002

Abstract Singly charged anionic clusters are exposed to a bath of simultaneously stored electrons in ion cyclotron resonance (Penning) traps and thus, dianions are produced. The dianion yield is found to be a function of the potential well depth. As an example, the attachment of electrons to size-selected gold cluster anions Au 25 1− from a laser vaporization source has been studied in detail by time-of-flight mass analysis after ejection of all ions from the trap. Furthermore, the investigation is extended to fullerene anions C 70 1− that are produced by laser desorption from a fullerene target in the external source of a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer…

Recent gold cluster studies in a Penning trap

2002

Abstract A progress report is given on the investigation of metal clusters with an ion cyclotron resonance (Penning) trap. The examples are taken from the recent studies on gold clusters. In particular, the monomer and dimer evaporation is monitored as a function of cluster size. For the particular case of Au 7 + this study is expanded to include the energy dependence of the branching ratio. In connection with the sequential decay of Au 8 + the information can be used for a model-free determination of the dissociation energy of Au 8 + . A second line of studies concerns the production, properties and storage behavior of polyanionic gold clusters. Such species have recently been produced by …

Collision induced dissociation of stored gold cluster ions

1994

The stability of gold cluster ions Au + (2≦n≦23) has been investigated via collision induced dissociation in a Penning trap. Threshold energies and dissociation channels have been determined. The cluster stability exhibits a pronounced odd — even alternation: Clusters with an odd number of atoms,n, are more stable than the even-numbered ones. Enhanced stabilities are found for Au 3 + , Au 9 + , and Au 19 + in accordance with the Clemenger-Nilsson and the deformed jellium model of delocalized valence electrons. Excited odd cluster ions withn≦15 predominantly decay by evaporation of dimers; all others decay by monomer evaporation. From the dissociation channels estimates of the binding energi…