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Biomedical subjects

C B Murray

Publications and source records attributed to C B Murray.

12 recordsLinked to original sources
PubMed2005

Bio-functionalization of monodisperse magnetic nanoparticles and their use as biomolecular labels in a magnetic tunnel junction based sensor.

Monodisperse magnetic nanoparticles (NPs) could enable the ultra-sensitive magnetic detection of biological analytes. However, rendering these particles biocompatible has remained a challenge. We report the bio-functionalization and detection of 12-nm manganese ferrite NPs. We have achieved the site-specific binding of biotin-functionalized NPs onto avidin-patterned silicon oxide substrates and DNA-functionalized NPs onto complementary DNA-patterned silicon oxide substrates. Utilizing scanning SQUID microscopy, we show that these substrate-bound NPs retain their magnetic properties. Finally, we demonstrate a novel method of detecting either protein binding or DNA hybridization at room temperature using the NPs and a magnetic tunnel-junction-based biosensor situated in orthogonal magnetic fields.

Avidin↗
PubMed2003

Three-dimensional binary superlattices of magnetic nanocrystals and semiconductor quantum dots.

Recent advances in strategies for synthesizing nanoparticles--such as semiconductor quantum dots, magnets and noble-metal clusters--have enabled the precise control of composition, size, shape, crystal structure, and surface chemistry. The distinct properties of the resulting nanometre-scale building blocks can be harnessed in assemblies with new collective properties, which can be further engineered by controlling interparticle spacing and by material processing. Our study is motivated by the emerging concept of metamaterials-materials with properties arising from the controlled interaction of the different nanocrystals in an assembly. Previous multi-component nanocrystal assemblies have usually resulted in amorphous or short-range-ordered materials because of non-directional forces or insufficient mobility during assembly. Here we report the self-assembly of PbSe semiconductor quantum dots and Fe2O3 magnetic nanocrystals into precisely ordered three-dimensional superlattices. The use of specific size ratios directs the assembly of the magnetic and semiconducting nanoparticles into AB13 or AB2 superlattices with potentially tunable optical and magnetic properties. This synthesis concept could ultimately enable the fine-tuning of material responses to magnetic, electrical, optical and mechanical stimuli.

Journal Article↗
PubMed2002

Polymer mediated self-assembly of magnetic nanoparticles.

We present a simple polymer-mediated process of assembling magnetic FePt nanoparticles on a solid substrate. Alternatively absorbing the PEI molecule and FePt nanoparticles on a HO-terminated solid surface leads to a smooth FePt nanoparticle assembly with controlled assembly thickness and dimension. Magnetic measurements show that the thermally annealed FePt nanoparticle assembly as thin as three nanoparticle layers is ferromagnetic. The magnetization direction of this thin FePt nanoparticle assembly is readily controlled with the laser-assisted magnetic writing. The reported process can be applied to various substrates, nanoparticles, and functional macromolecules and will be useful for future magnetic nanodevice fabrication.

Journal Article↗
PubMed2000

Spin-dependent tunneling in self-assembled cobalt-nanocrystal superlattices.

Self-assembled devices composed of periodic arrays of 10-nanometer-diameter cobalt nanocrystals display spin-dependent electron transport. Current-voltage characteristics are well described by single-electron tunneling in a uniform array. At temperatures below 20 kelvin, device magnetoresistance ratios are on the order of 10%, approaching the maximum predicted for ensembles of cobalt islands with randomly oriented preferred magnetic axes. Low-energy spin-flip scattering suppresses magnetoresistance with increasing temperature and bias-voltage.

Journal Article↗
PubMed2000

Effects of parental marital status, income, and family functioning on African American adolescent self-esteem.

This study examined the effects of marital status, family income, and family functioning on African American adolescents' self-esteem. One hundred sixteen adolescents participated, 64% of whom were female. Compared with boys with nonmarried parents, boys with married parents had higher overall self-esteem, even when family income and family functioning were controlled. Parental marital status had no effect on girls' self-esteem. Family functioning was a very strong predictor of self-esteem for both sexes. However, family relational factors were more important to girls' self-esteem, whereas structural and growth factors were more important for boys. It was concluded that African American adolescent boys with nonmarried parents are at risk for developing low self-esteem compared with other African American adolescents, but a more controlled and structured environment may buffer the effects of having nonmarried parents.

Adolescent↗
PubMed1996

A short CIC-2 mRNA transcript is produced by exon skipping.

CIC-2 is a voltage- and volume-regulated chloride channel expressed in many tissues. We have shown that CIC-2 in rat lung airways is significantly down-regulated after birth [Murray,C.B. et al. (1995) Am. J. Respir. Cell Mol. Biol., 12, 597-604]. During PCR amplification from rat lung cDNA, a second transcript was identified which is 60 bp shorter than the full length sequence. The peptide translated from this 60 bp sequence contains many positively charged amino acid residues. Rat genomic DNA sequencing showed that the 60 bp sequence is an intact exon. A 71% pyrimidine content and an AAG 3'-end splice site in the intron immediately upstream from the 60 bp sequence were identified which may account for the alternative splicing of the following exon. Human genomic sequence analyses demonstrated similar intron-exon arrangement. A high CT content and an AAG 3' acceptor site were conserved in the intron corresponding to the rat upstream intron. The presence of the full length short form transcript was confirmed in rat kidney by RT-PCR, and the ratio of the long and the short form transcripts varied significantly according to the tissues examined, with the lowest long/short form ratio found in the lung among the tissues studied. Our data demonstrated that the alternatively spliced short form (CIC-2S) is transcribed in many rat tissues, the ratio of the long/short form transcripts is lower in the lung compared with the brain, and the genomic organization in this area is conserved in rat and human.

Alternative Splicing↗
PubMed1996

Gestational and tissue-specific regulation of C1C-2 chloride channel expression.

Chloride channels supply critical functions in epithelial cells throughout the body. Although function of the volume- and voltage-gated C1C-2 is uncertain, its wide tissue distribution of mRNA suggests C1C-2 has important housekeeping functions. This study's objective was to identify the extent of not only C1C-2 mRNA expression but also protein expression as a measure of the capacity for C1C-2 chloride secretion in epithelial tissues. Using quantitative ribonuclease protection assay, we found that C1C-2 mRNA transcripts were abundant in fetal and postnatal brain, fetal kidney, liver, intestine, and lung. In contrast to brain, C1C-2 mRNA transcripts were downregulated during late gestation in lung, kidney, and intestine. The lung expressed the least C1C-2 mRNA. Immunoblotting demonstrated similar tissue- and gestation-dependent variations in C1C-2 protein expression. To determine if there is a correlation between the sites of C1C-2 protein expression and cystic fibrosis transmembrane conductance regulator (CFTR), another epithelial chloride channel, a polyclonal COOH-terminal C1C-2 antibody and an anti-R domain CFTR anti-body were used. C1C-2 and CFTR were expressed in different sites in lung and kidney.

Aging↗
PubMed1995

CIC-2: a developmentally dependent chloride channel expressed in the fetal lung and downregulated after birth.

Growth and differentiation of the fetal lung are dependent on chloride and fluid secretion, yet the specific molecular identities of fetal chloride channels have not been fully determined. In this study, we demonstrate mRNA expression of the volume-activated chloride channel, CIC-2, in fetal rat lung using reverse-transcriptase polymerase chain reaction (RT-PCR) and ribonuclease (RNase) protection assay. By RNase protection assay, CIC-2 mRNA expression is most abundant in fetal lung and diminishes after birth until it is almost undetectable in adult rat lung. To confirm this result at the protein level, a C-terminal fragment of CIC-2 cDNA derived from 19-day fetal rat lung was cloned into an expression plasmid. The truncated 33-kD CIC-2 protein was expressed in Escherichia coli and purified by column chromatography. Polyclonal antibodies to this antigen were raised in chickens, and the antisera detected a 94-kD protein in fetal rat lung homogenates by Western blotting. Protein expression of CIC-2 was most abundant in mid and late gestation and decreased significantly shortly after birth, as would be predicted by the RNase protection data. CIC-2 protein was localized along the apical surface of fetal airway epithelium by immunocytochemistry. The abundant fetal expression of CIC-2 RNA and protein supports the hypothesis that CIC-2 is important to fetal lung development, and its apical location suggests that it may be involved in fluid secretion during normal lung morphogenesis.

Animals↗
PubMed1995

Making the most of pulse oximetry.

A noninvasive device that gives continuous oxygenation readings has great appeal, and pulse oximetry has enjoyed wide acceptance. To use it most effectively, though, you need to understand the principles it's based on and know its limitations.

Ambulatory Care↗
PubMed1988

A genetic analysis of body size in pink salmon (Oncorhynchus gorbuscha).

Two small-sized and two large-sized male pink salmon (Oncorhynchus gorbuscha) were mated to each of four females, producing eight families sired by small males and eight sired by large males. The juveniles were reared for 500 d after fry emergence. Juvenile weight in the two male size classes was similar until the spring of the year of maturity, when juveniles sired by large males grew faster than those sired by small ones. Heritability estimates of weight based upon the dam component of variance increased during 500 d of rearing from 0.4 to 0.8. Heritability of weight based upon the sire component of variance generally ranged between 0.1 and 0.3. The large variation in male body size in spawning pink salmon populations may have resulted from different male breeding strategies.

Animals↗
PubMed1988

Genetic analysis of growth and maturity in pink salmon (Oncorhynchus gorbuscha).

Variation in growth and sexual maturity was examined for five stocks of pink salmon (Oncorhynchus gorbuscha) spawning at different times in British Columbia. In each stock, four males were mated with eight females in a nested breeding design, and the juveniles were reared for 500 d after fry emergence. Adults in early-spawning northern stocks were smaller than those in late-spawning southern ones, but pink salmon from northern stocks had faster growth rates than those from southern ones. The relative ranking within stocks of family weight remained constant after late winter in the year of maturity. Heritability of weight based upon sire variance components was usually greater than 0.9 after 150 d of rearing. Pink salmon from the earlier-spawning stocks were in a more advanced state of sexual maturity when the experiment was terminated than were those from later-spawning stocks, indicative of a significant genetic component in timing of sexual maturity.

Aging↗