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A Sterling

Publications and source records attributed to A Sterling.

16 recordsLinked to original sources
PubMed2006

Selectivity of tryptophan residues in mediating photolysis of disulfide bridges in goat alpha-lactalbumin.

Goat alpha-lactalbumin (GLA) contains four tryptophan (Trp) residues and four disulfide bonds. Illumination with near-UV light results in the cleavage of disulfide bridges and in the formation of free thiols. To obtain information about the reaction products, the illuminated protein was carbamidomethylated and digested with trypsin and the peptides were analyzed by mass spectrometry. Peptides containing Cys120Cam, Cys61Cam, or Cys91Cam were detected, as well as two peptides containing a new Cys-Lys cross-link. In one, Cys6 was cross-linked to Lys122, while the cross-link in the second was either a Cys91-Lys79 or Cys73-Lys93 cross-link; however, the exact linkage could not be defined. The results demonstrate photolytic cleavage of the Cys6-Cys120, Cys61-Cys77, and Cys73-Cys91 disulfide bonds. While photolysis of Cys6-Cys120 and Cys73-Cys91 disulfide bonds in GLA has been reported, cleavage of the Cys61-Cys77 disulfide bonds has not been previously detected. To examine the contribution of the individual Trp residues, we constructed the GLA mutants, W26F, W60F, W104F, and W118F, by replacing single Trp residues with phenylalanine (Phe). The substitution of each Trp residue led to less thiol production compared to that for wild-type GLA, showing that each Trp residue in GLA contributed to the photolytic cleavage of disulfide bridges. The specificity was expressed by the nature of the reaction products. No cleavage of the Cys6-Cys120 disulfide bridge was detected when the W26F mutant was illuminated, and no cleavage of the Cys73-Cys91 disulfide bridge was seen following illumination of W26F or W104F. In contrast, Cys61Cam, resulting from the cleavage of the Cys61-Cys77 disulfide bridge, was found following illumination of any of the mutants.

Amino Acid Sequence↗
PubMed2004

Metabolite fingerprinting: detecting biological features by independent component analysis.

MOTIVATION: Metabolite fingerprinting is a technology for providing information from spectra of total compositions of metabolites. Here, spectra acquisitions by microchip-based nanoflow-direct-infusion QTOF mass spectrometry, a simple and high throughput technique, is tested for its informative power. As a simple test case we are using Arabidopsis thaliana crosses. The question is how metabolite fingerprinting reflects the biological background. In many applications the classical principal component analysis (PCA) is used for detecting relevant information. Here a modern alternative is introduced-the independent component analysis (ICA). Due to its independence condition, ICA is more suitable for our questions than PCA. However, ICA has not been developed for a small number of high-dimensional samples, therefore a strategy is needed to overcome this limitation. RESULTS: To apply ICA successfully it is essential first to reduce the high dimension of the dataset, by using PCA. The number of principal components determines the quality of ICA significantly, therefore we propose a criterion for estimating the optimal dimension automatically. The kurtosis measure is used to order the extracted components to our interest. Applied to our A. thaliana data, ICA detects three relevant factors, two biological and one technical, and clearly outperforms the PCA.

Algorithms↗
PubMed2001

Seasonal variations in radionuclide transfer in a Mediterranean grazing-land ecosystem.

We made quarterly determinations of the transfer coefficients and effective transfer coefficients for the radionuclides 137Cs, 90Sr, 40K, 226Ra, 228Ra and 228Th over a full annual cycle, in a Mediterranean grazing-land ecosystem. The input and output fluxes of the radionuclides between the different compartments of this ecosystem were quantified for the following processes: root uptake; variation in root and aerial biomass; pasture production; translocation; leaf fall; efflux due to grazing action; resuspension and subsequent aerial deposition of radionuclides. We observed there to be a marked seasonal variation for this type of ecosystem in both the transfer coefficients and the radionuclide fluxes, which impedes the soil-plant transfer being characterized on the basis of values that are constant with time.

Ecosystem↗
PubMed1999

Radiocaesium and radiostrontium uptake by turnips and broad beans via leaf and root absorption.

One of the immediate consequences of massive radioisotope release into the atmosphere is contamination of the biosphere. This contamination can affect plants either by direct deposition onto the leaves, or by contaminating the soil followed by absorption by the roots. Knowledge of the efficacy of the two routes of radionuclide incorporation into the food chain is fundamental to understanding the mechanisms by which radioactive contamination reaches man. The present work analyzes the incorporation of 134Cs and 85Sr via root and leaf uptake into the parts consumed by man, for two very different crops: turnip (Brassica napus) and broad bean (Vicia faba). The root uptake studies consider the available soil fraction for these two radionuclides, and indicate greater availability for 85Sr than for 134Cs which is fixed rapidly in the soil. For the study of leaf uptake, leaves were contaminated at three different stages of plant growth; the results indicate an inverse dependence of the transfer coefficients on the time elapsed from the moment of the contamination to harvesting of the edible parts.

Air Pollutants, Radioactive↗
PubMed1998

Atractyloside-induced release of cathepsin B, a protease with caspase-processing activity.

Recent data show that a strong relation exists in certain cells between mitochondria and caspase activation in apoptosis. We further investigated this relation and tested whether treatment with the permeability transition (PT)-inducing agent atractyloside of Percoll-purified mitochondria released a caspase-processing activity. Following detection of procaspase-11 processing, we further purified this caspase-processing protease and identified it as cathepsin B. The purified cathepsin B, however, was found to be derived from lysosomes which were present as minor contaminants in the mitochondrial preparation. Besides procaspase-11, caspase-1 is also readily processed by cathepsin B. Procaspase-2, -6, -7, -14 are weak substrates and procaspase-3 is a very poor substrate, while procaspase-12 is no substrate at all for cathepsin B. In addition, cathepsin B induces nuclear apoptosis in digitonin-permeabilized cells as well as in isolated nuclei. All newly described activities of cathepsin B, namely processing of caspase zymogens and induction of nuclear apoptosis, are inhibited by the synthetic peptide caspase inhibitors z-VAD.fmk, z-DEVD.fmk and to a lesser extent by Ac-YVAD.cmk.

Amino Acid Sequence↗
PubMed1997

Alpha-latrotoxin receptor, latrophilin, is a novel member of the secretin family of G protein-coupled receptors.

alpha-Latrotoxin (LTX) stimulates massive exocytosis of synaptic vesicles and may help to elucidate the mechanism of regulation of neurosecretion. We have recently isolated latrophilin, the synaptic Ca2+-independent LTX receptor. Now we demonstrate that latrophilin is a novel member of the secretin family of G protein-coupled receptors that are involved in secretion. Northern blot analysis shows that latrophilin message is present only in neuronal tissue. Upon expression in COS cells, the cloned protein is indistinguishable from brain latrophilin and binds LTX with high affinity. Latrophilin physically interacts with a Galphao subunit of heterotrimeric G proteins, because the two proteins co-purify in a two-step affinity chromatography. Interestingly, extracellular domain of latrophilin is homologous to olfactomedin, a soluble neuronal protein thought to participate in odorant binding. Our findings suggest that latrophilin may bind unidentified endogenous ligands and transduce signals into nerve terminals, thus implicating G proteins in the control of synaptic vesicle exocytosis.

Amino Acid Sequence↗
PubMed1997

Aneurysm of the radial artery following blunt trauma to the wrist.

Aneurysms involving the distal radial artery are rare lesions which are usually secondary to penetrating trauma or iatrogenic injury. Blunt trauma is an extremely uncommon cause. In the absence of a history of penetrating vascular injury, a radial artery aneurysm may easily be misdiagnosed as a nonvascular mass such as a synovial cyst. A diagnostic approach to these lesions is discussed emphasizing the role of noninvasive studies in uncomplicated cases. Excision of the aneurysm is recommended. The decision to ligate or reconstruct the radial artery remains controversial.

Aged↗
PubMed1977

Post-traumatic cysts of soft tissue.

Post-traumatic cysts of soft tissue, formed by crushing and shearing strains, usually occur at the junction of the subcutaneous fat and deep fascia. They become filled with serosanguinous fluid and lined with fibrous tissue. Chronic cysts may either remain stable or occasionally expand, much like a subdural hematoma.

Adipose Tissue↗
PubMed1976

The standardization of terminology of lower urinary tract function.

The terminology of lower urinary tract function will be standardized by the ICS. This report contains the recommendations dealing with urinary incontinence, procedures related to the evaluation of urine storage (cystometry, urethral closure pressure profile) and units of measurement.

Compliance↗