Biomedical subjects

H X You

Publications and source records attributed to H X You.

8 recordsLinked to original sources

PubMed2001

Phospholipid membrane restructuring induced by saposin C: a topographic study using atomic force microscopy.

The enzymatic activity of glucosylceramidase depends on the presence of saposin C (Sap C) and acidic phospholipid-containing membranes. In order to delineate the mechanism underlying Sap C stimulation of the enzyme activity, it is important to understand how Sap C interacts with phospholipid membranes. We studied the dynamic process of Sap C interaction with planar phospholipid membranes, in real time, using atomic force microscopy (AFM). The phospholipid membrane underwent restructuring upon addition of Sap C. The topographic characteristics of the membrane restructuring include the appearance of patch-like new features, initially emerged at the edge of phospholipid membranes and extended laterally with time. Changes in the image contrast of the phospholipid membrane observed after the Sap C addition indicate that a new phase of lipid-protein structure has formed during membrane restructuring. The process of membrane restructuring is dynamic, commencing shortly after Sap C addition, and continuing throughout the duration of AFM imaging (about 30 min, sometimes over 1 h). This study demonstrated the potential of AFM real-time imaging in studying protein-membrane interactions.

Glycoproteins↗

PubMed2000

Atomic force microscopy imaging of living cells: a preliminary study of the disruptive effect of the cantilever tip on cell morphology.

Recent studies have demonstrated that atomic force microscopy (AFM) is a potential tool for studying important dynamic cellular processes in real time. However, the interactions between the cantilever tip and the cell surface are not well understood, and the disruptive effect of the cantilever tip on cell morphology has not been well characterized. In this study, the disruptive effect of the scanning cantilever tip on cell morphology, in the AFM contact mode, has been investigated. The aims of this study are to identify what kinds of cell morphological changes generally occurred under normal AFM imaging conditions and to find out how long cells remain viable during scanning. Two cell lines, SK-N-SH (human neuroblastoma cells) and AV12 (Syrian hamster cells) were studied in the experiment because these are widely used in biomedical research as an expression system for studying cellular functions of neuronal receptors. The experimental results suggest that the sensitivity of cells to the cantilever disruptive effect is dependent on cell type and that there are patterns observed in the changes of cell morphology induced by the cantilever force in these two cell lines.

Animals↗

PubMed1999

Atomic force microscopy imaging of living cells: progress, problems and prospects.

Recent development of atomic force microscopy (AFM) applications in imaging living cells is reviewed, focusing on technical progress and application advancements made in the following major areas: (i) high-resolution imaging of cellular structures, (ii) real-time monitoring of cellular dynamic processes, and (iii) detecting micromechanical properties of the cell. Technical and experimental difficulties frequently encountered in AFM applications in above areas are presented and possible strategies for overcoming these obstacles are discussed. Significant advances in the AFM study of living cells can be achieved from further development of AFM technology, sample preparation, and innovative applications.

Air↗

PubMed1998

Covalent coupling of immunoglobulin G to self-assembled monolayers as a method for immobilizing the interfacial-recognition layer of a surface plasmon resonance immunosensor.

Protocols have been developed for the random and site-directed covalent coupling of immunoglobulin G [anti-hIgG] [IgG] to silver surfaces modified with a self-assembled monolayer [SAM] of thioctic acid, mercaptopropionic acid [MPA], L-cysteine or 4-aminothiophenol [PATP]. A surface plasmon resonance [SPR] immunosensor fabricated with a more ordered and hydrophilic IgG-SAM-silver interfacial layer, demonstrates an increased ability for performing sensitive and selective assay of human immunoglobulin G [hIgG] compared with a device fabricated with a physically-adsorbed IgG-silver interfacial-layer due to reduced levels of non-specific binding. Detection limits [DL] for hIgG from serum down to 6 micrograms/ml (40 nM) and assay sensitivities up to 0.24 ng hIgG/mm2/nM are reported.

Biosensing Techniques↗

PubMed1998

Covalent coupling of immunoglobulin G to a poly(vinyl)alcohol-poly(acrylic acid) graft polymer as a method for fabricating the interfacial-recognition layer of a surface plasmon resonance immunosensor.

The synthesis of a terminally thiolated poly(vinyl)alcohol (PVA) grafted with Poly (acrylic acid) (PAA) side chains is described. The PVA-PAA graft polymer (PVAg) was end-tethered to silver surfaces via the terminal thiol functionality and the resultant mobile, hydrophilic polymer matrix exploited for the covalent immobilization of large quantities of polyclonal goat (anti-hIgG) antibody (IgG) with low levels of non-specific adsorption. An SPR immunosensor, fabricated with an IgG-PVA-silver interfacial layer proved capable of performing a sensitive label-free assay of human IgG antigen (hIgG) with minimal non-specific binding interference. A detection limit (DL) for hIgG from serum of 0.8 microgram/ml (5 nM) and an assay sensitivity of 0.66 ng hIgG/mm2/nM are reported.

Acrylic Resins↗

PubMed1995

A scanning tunnelling microscopic study of site-specifically immobilized immunoglobulin G on gold.

A convenient and efficient method for the site-specific incorporation of foreign cysteine residues at the C-termini of immunoglobulin G (IgG) using carboxypeptidase-Y-catalyzed transpeptidation is explored as a means of ensuring oriented immobilization of IgG on gold. A scanning tunnelling microscopic study of the immobilization of the modified IgG molecules on gold surfaces is reported. The results show not only that some globular features are observed to form striking surface patterns with a geometric size close to that of the fragments of IgG but also that the conformation of the bound IgG molecules appears more stable when adsorbed on gold. The effect of the immobilization method on these topographic features is discussed.

Animals↗

PubMed1994

Physical adsorption of immunoglobulin G on gold studied by scanning tunnelling microscopy.

This paper describes a preliminary scanning tunnelling microscope (STM) study of the physical adsorption of a mouse monoclonal anti-hCG (human chorionic gonadotrophin) immunoglobulin G (IgG) on vacuum-evaporated gold surfaces in air. Ellipsoid-like protrusions of various geometric sizes assembled in different surface patterns were observed on scanning adsorbed IgG molecules. It is believed that both the adsorption process per se and the tip-molecule interactions are key factors which determine the topographical features of adsorbed IgG molecules.

Adsorption↗

PubMed1991

A preliminary scanning tunnelling microscopy study of the surface-organised structures of gramicidin S hydrochloride on highly oriented pyrolytic graphite.

For an initial study of potentially surface-structural self-organising systems of biological significance by scanning tunnelling microscopy (STM), gramicidin S, a pseudocentrosymmetric cyclodecapeptide with antibiotic properties, was chosen as prototype, recognising its structure as having both intramolecular and intermolecular hydrogen-bond forming propensity. The surface-organised structures, based on gramicidin S hydrochloride deposited on a highly oriented pyrolytic graphite (HOPG) substrate, have been observed by STM in air under ambient conditions. These are characterised in the main by rectangular or rectangle-like structural elements identified with the individual gramicidin S hydrochloride molecules. Two kinds of arrangements of gramicidin S hydrochloride in a two-dimensional array are found, i.e., as a centred rectangular lattice and a primitive rectangular lattice. The STM topographical arrays and the molecular dimensions obtained are in good quantitative agreement with the corresponding X-ray crystallographic data. The differences between the STM results, the theoretical models, and the X-ray crystallographic data are attributed to the intermolecular interactions present in the three-dimensional gramicidin S crystal but absent in the lower dimensional arrays and to the environments in which a gramicidin S hydrochloride molecule finds itself during deposition and drying on the HOPG substrate.

Amino Acid Sequence↗