Home About us Contact
|
Home About us Contact | ||
|
|
||
Protein Size (protein + size)
Selected AbstractsDevelopmental variation in epidermal growth factor receptor size and localization in the malaria mosquito, Anopheles gambiaeINSECT MOLECULAR BIOLOGY, Issue 6 2001G. Lycett Abstract The AGER gene encoding the epidermal growth factor receptor (EGFR) of the malaria mosquito Anopheles gambiae was cloned and sequenced. It represents a canonical member of this family of tyrosine kinase proteins exhibiting many similarities to orthologues from other species, both on the level of genomic organization and protein structure. The mRNA can be detected throughout development. Western analysis with an antibody raised against the extracellular domain of the mosquito protein suggests developmental variation in protein size and location that may be involved in the function of EGFR in the mosquito. [source] Measurement of Lens Protein Aggregation in Vivo Using Dynamic Light Scattering in a Guinea Pig/UVA Model for Nuclear CataractPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2008M. Francis Simpanya The role of UVA radiation in the formation of human nuclear cataract is not well understood. We have previously shown that exposing guinea pigs for 5 months to a chronic low level of UVA light produces increased lens nuclear light scattering and elevated levels of protein disulfide. Here we have used the technique of dynamic light scattering (DLS) to investigate lens protein aggregation in vivo in the guinea pig/UVA model. DLS size distribution analysis conducted at the same location in the lens nucleus of control and UVA-irradiated animals showed a 28% reduction in intensity of small diameter proteins in experimental lenses compared with controls (P < 0.05). In addition, large diameter proteins in UVA-exposed lens nuclei increased five-fold in intensity compared to controls (P < 0.05). The UVA-induced increase in apparent size of lens nuclear small diameter proteins was three-fold (P < 0.01), and the size of large diameter aggregates was more than four-fold in experimental lenses compared with controls. The diameter of crystallin aggregates in the UVA-irradiated lens nucleus was estimated to be 350 nm, a size able to scatter light. No significant changes in protein size were detected in the anterior cortex of UVA-irradiated lenses. It is presumed that the presence of a UVA chromophore in the guinea pig lens (NADPH bound to zeta crystallin), as well as traces of oxygen, contributed to UVA-induced crystallin aggregation. The results indicate a potentially harmful role for UVA light in the lens nucleus. A similar process of UVA-irradiated protein aggregation may take place in the older human lens nucleus, accelerating the formation of human nuclear cataract. [source] Probing protein structure and dynamics by second-derivative ultraviolet absorption analysis of cation,, interactionsPROTEIN SCIENCE, Issue 10 2006Laura H. Lucas Abstract We describe an alternate approach for studying protein structure using the detection of ultraviolet (UV) absorbance peak shifts of aromatic amino acid side chains induced by the presence of salts. The method is based on the hypothesis that salt cations (Li+, Na+, and Cs+) of varying sizes can differentially diffuse through protein matrices and interact with benzyl, phenyl, and indole groups through cation,, interactions. We have investigated the potential of this method to probe protein dynamics by measuring high resolution second-derivative UV spectra as a function of salt concentration for eight proteins of varying physical and chemical properties and the N -acetylated C -ethyl esterified amino acids to represent totally exposed side chains. We show that small shifts in the wavelength maxima for Phe, Tyr, and Trp in the presence of high salt concentrations can be reliably measured and that the magnitude and direction of the peak shifts are influenced by several factors, including protein size, charge, and the local environment and solvent accessibility of the aromatic groups. Evaluating the empirical UV spectral data in light of known protein structural information shows that probing cation,, interactions in proteins reveals unique information about the influence of structure on aromatic side chain spectroscopic behavior. [source] Ultrafiltration characteristics of pegylated proteinsBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2006Jessica R. Molek Abstract There is growing clinical interest in the use of pegylated recombinant proteins with enhanced stability, half-life, and bioavailability. The objective of this study was to develop a quantitative understanding of the ultrafiltration characteristics of a series of pegylated proteins with different degrees of pegylation. Sieving data were compared with available theoretical models and with corresponding results for the partition coefficient in size exclusion chromatography (SEC). The sieving coefficients of the pegylated proteins depended not only on the protein size and the total molecular weight of the polyethylene glycol (PEG) but also on the number of PEG chains. This is in sharp contrast to the partition coefficient in SEC, which was uniquely determined by the total molecular weight of the PEG and protein. This difference is due to the deformation and/or elongation of the PEG chains caused by the convective flow into the membrane pores, an effect that is not present in SEC. These results provide important insights into the transport and separation characteristics of pegylated proteins. © 2006 Wiley Periodicals, Inc. [source] Identification and Characterisation of a Platelet GPIb/V/IX-like Complex on Human Breast Cancers: Implications for the Metastatic ProcessCANCER SCIENCE, Issue 10 2001Catherine M. Suter The glycoprotein (GP) Ib/V/IX receptor complex is an important adhesion molecule, originally thought to be unique to the megakaryocytic lineage. Recent evidence now indicates that GPIb/V/IX may be more widely expressed. In this study we report the presence of all subunits of the complex on four breast cancer cell lines, and 51/80 primary breast tumours. The surface expression of GPIb/V/IX was confirmed by flow cytometry, and by immunoprecipitation of biotin surface-labelled tumour cells. Western blotting of cell lysates under reducing conditions revealed that tumour cell-GPIba had a relative molecular weight of 95 kDa as compared to 135 kDa on platelets. Despite the discrepant protein size, molecular analyses on the tumour cell-GPIba subunit using RT-PCR and DNA sequencing revealed 100% sequence homology to platelet GPIba. Tumour cell-GPIb/V/IX was capable of binding human von Willebrand factor (vWf), and this binding caused aggregation of tumour cells in suspension. Tumour cells bound to immobilised vWf in the presence of EDTA and demonstrated prominent filapodial extensions indicative of cytoskeletal reorganisation. Furthermore, in a modified Boyden chamber assay, prior exposure to vWf or a GPIba monoclonal antibody, AK2, enhanced cell migration. The presence of a functional GPIb/V/IX-like complex in tumour cells suggests that this complex may participate in the process of haematogenous breast cancer metastasis [source] The characterization of versican and its message in human articular cartilage and intervertebral discJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2002Robert Sztrolovics Splicing variation of the versican message and size heterogeneity of the versican core protein were analyzed in human articular cartilage and intervertebral disc. Splicing variation of the message was studied by PCR analysis to detect the presence or absence of exons 7 and 8, which encode large chondroitin sulfate attachment regions. At all ages in normal cartilage from the third trimester fetus to the mature adult, the presence of the versican isoform possessing exon 8 but not exon 7 (V1) could be readily detected. The message isoforms possessing neither exon 7 nor 8 (V3) or both exons 7 and 8 (V0) were only detectable in the fetus, and the isoform possessing only exon 7 (V2) was never detected. In osteoarthritic cartilage and in adult intervertebral disc the versican message pattern was the same as that observed in the normal adult with only the isoform possessing exon 8 being detected. Core protein heterogeneity was studied by immunoblotting following enzymic removal of the glycosaminoglycan chains from the proteoglycan, using an antibody recognizing the globular G1 region of versican. All articular cartilage extracts from the fetus to the mature adult contained multiple core protein sizes of greater than 200 kDa. The adult cartilage extracts tended to have an increased proportion of the smaller sized core proteins and osteoarthritic cartilage possessed similar core protein sizes to the normal adult. In contrast, intervertebral disc at all post-natal ages showed a greater range of size heterogeneity with a prominent component of about 50 kDa. The abundance of this component increased if the samples were treated with keratanase prior to analysis, suggesting that the G1 region of versican in disc can be substituted with keratan sulfate. The increased presence of versican in the disc relative to articular cartilage may suggest a more pronounced functional role for this proteoglycan, particularly in the nucleus pulposus. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] | ||||||||||