| 1. |
- Hilson, P., et al.
(författare)
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Versatile gene-specific sequence tags for Arabidopsis functional genomics : Trancript profiling and reverse genetics applications
- 2004
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 14:10B, s. 2176-2189
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Tidskriftsartikel (refereegranskat)abstract
- Microarray transcript profiling and RNA interference are two new technologies crucial for large-scale gene function studies in multicellular eukaryotes. Both rely on sequence-specific hybridization between complementary nucleic acid strands, inciting us to create a collection of gene-specific sequence tags (GSTs) representing at least 21,500 Arabidopsis genes and which are compatible with both approaches. The GSTs were carefully selected to ensure that each of them shared no significant similarity with any other region in the Arabidopsis genome. They were synthesized by PCR amplification from genomic DNA. Spotted microarrays fabricated from the GSTs show good dynamic range, specificity, and sensitivity in transcript profiling experiments. The GSTs have also been transferred to bacterial plasmid vectors via recombinational cloning protocols. These cloned GSTs constitute the ideal starting point for a variety of functional approaches, including reverse genetics. We have subcloned GSTs on a large scale into vectors designed for gene silencing in plant cells. We show that in planta expression of GST hairpin RNA results in the expected phenotypes in silenced Arabidopsis lines. These versatile GST resources provide novel and powerful tools for functional genomics.
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| 2. |
- Jacobson, Peter, 1962, et al.
(författare)
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Melanocortin 4 receptor sequence variations are seldom a cause of human obesity: the Swedish Obese Subjects, the HERITAGE Family Study, and a Memphis cohort.
- 2002
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Ingår i: The Journal of clinical endocrinology and metabolism. - 0021-972X. ; 87:10, s. 4442-6
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Tidskriftsartikel (refereegranskat)abstract
- The prevalence of mutations within and in the flanking regions of the gene encoding the melanocortin 4 receptor was investigated in severely obese and normal-weight subjects from the Swedish Obese Subjects study, the Health, Risk Factors, Exercise Training, and Genetics (HERITAGE) Family study, and a Memphis cohort. A total of 433 white and 95 black subjects (94% females) were screened for mutations by direct sequencing. Three previously described missense variants and nine novel (three missense, six silent) variants were detected. None of them showed significant association with obesity or related phenotypes. In addition, two novel deletions were found in two heterozygous obese women: a -65_-64delTG mutation within the 5' noncoding region and a 171delC frameshift mutation predicted to result in a truncated nonfunctional receptor. No pathogenic mutations were found among obese blacks or nonobese controls. Furthermore, none of the null mutations found in other populations was present in this sample. In conclusion, our results do not support the prevailing notion that sequence variation in the melanocortin 4 receptor gene is a frequent cause of human obesity.
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| 3. |
- Leon, R., et al.
(författare)
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Defect states in red-emitting InxAl1-xAs quantum dots
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 66:8
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Tidskriftsartikel (refereegranskat)abstract
- Optical and transport measurements carried out in pn diodes and Schottky barriers containing multilayers of InAlAs quantum dots embedded in AlGaAs barriers show that while red emission from quantum dot (QD) states is obtained at similar to1.8 eV, defect states dominate the optical properties and transport in these quantum dots. These defects provide nonradiative recombination paths, which shortens the carrier lifetimes in QD's to tens of picoseconds (from similar to1 ns) and produce deep level transient spectroscopy (DLTS) peaks in both p and n type structures. DLTS experiments performed with short filling pulses and bias dependent measurements on InAlAs QD's on n-AlGaAs barriers showed that one of the peaks can be attributed to either QD/barrier interfacial defects or QD electron levels, while other peaks are attributed to defect states in both p and n type structures.
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| 4. |
- Leon, Rosa, et al.
(författare)
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Dislocation-induced spatial ordering of InAs quantum dots : Effects on optical properties
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:9, s. 5826-5830
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Tidskriftsartikel (refereegranskat)abstract
- Misfit dislocations were used to modify the surface morphology and to attain spatial ordering of quantum dots (QDs) by molecular beam epitaxy. Effects of anneal time and temperature on strain-relaxed InxGa1-xAs/GaAs layers and subsequent spatial ordering of InAs QDs were investigated. Photoluminescence (PL) and time-resolved PL was used to study the effects of increased QD positional ordering, increased QD uniformity, and their proximity to dislocation arrays on their optical properties. Narrower inhomogeneous PL broadening from the QDs ordered on dislocation arrays were observed, and differences in PL dynamics were found.
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| 5. |
- Siegert, Jörg, et al.
(författare)
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Carrier recombination in aligned InAs/GaAs quantum dots grown in strain-relaxed InGaAs layers
- 2003
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley. - 1610-1634 .- 1610-1642. ; 0:4, s. 1213-
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Tidskriftsartikel (refereegranskat)abstract
- Alignment of InAs quantum dots was achieved by introducing misfit dislocations in a metastable InGaAs layer and subsequent annealing. Photoexcited carrier dynamics were studied using time-resolved photoluminescence. Comparison with control “non-aligned” InAs quantum dots show remarkable differences in integrated photoluminescence intensities with excitation power and photoluminescence decay time dependences on excitation intensities. Low-temperature carrier lifetimes were found to be below one hundred picoseconds for the aligned quantum dots and to be determined by non-radiative recombination processes. Samples with different barrier thicknesses between the InGaAs and the quantum dot layer allow the discussion of possible influences of carrier traps at InGaAs/GaAs interface and in the dot layer.
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| 6. |
- Siegert, Jörg, et al.
(författare)
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Photoexcited carrier dynamics in aligned InAs/GaAs quantum dots grown on strain-relaxed InGaAs layers
- 2003
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - 1386-9477 .- 1873-1759. ; 18:4, s. 541-
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Tidskriftsartikel (refereegranskat)abstract
- Carrier dynamics in aligned InAs/GaAs quantum dots (QDs) grown on cross-batched patterns induced by metastable InxGa1-xAs layers have been studied by time-resolved photoluminescence. The low-temperature carrier lifetimes were found to be of the order of 100-200 ps and determined by carrier trapping and nonradiative recombination. Comparisons with control "nonaligned" InAs QDs show remarkable differences in dependence of peak PL intensities on excitation power, and in PL decay times dependences on both temperature and excitation intensities. Possible origin of traps, which determine the carrier lifetimes, is discussed.
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| 7. |
- Ukkola, Olavi, et al.
(författare)
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Role of ghrelin polymorphisms in obesity based on three different studies.
- 2002
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Ingår i: Obesity research. - : Wiley. - 1071-7323. ; 10:8, s. 782-91
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Associations between preproghrelin DNA variants and obesity-related phenotypes were studied in 3004 subjects from the Québec Family Study (QFS), the HERITAGE Family Study (HERITAGE), and the Swedish Obese Subjects (SOS) Study. RESEARCH METHODS AND PROCEDURES: Body mass index (BMI), fat mass (FM) from underwater weighing, and abdominal fat from computerized tomography were measured. The ghrelin polymorphisms were identified by polymerase chain reaction. RESULTS: Arg51Gln QFS subjects (n = 6) had lower ghrelin concentrations (p = 0.007) than Arg51Arg subjects (n = 14). White preproghrelin Met72Met subjects in HERITAGE had the lowest BMI (p = 0.020), and those in the QFS cohort had the lowest FM (p < 0.001). Met72 carrier status (Met72+) was associated with lower FM (p = 0.026) and higher insulin-like growth factor-1 levels (p = 0.019) among blacks. Met72Met QFS subjects had less visceral fat (p = 0.002) and a lower fasting respiratory quotient (p = 0.037). HERITAGE Met72+ white subjects also showed lower exercise respiratory quotient (p = 0.030) and higher maximal oxygen uptake (p = 0.023). Furthermore, the prevalence of Met72+ was higher (19.2%; p < 0.05) in SOS subjects whose BMI was < or =25 kg/m(2) than in those with BMI >25 kg/m(2) (14.8%). SOS Met72+ obese women had a lower (11.4%; p = 0.032) prevalence of hypertension than noncarriers (23.9%). DISCUSSION: Arg51Gln mutation was associated with lower plasma ghrelin levels but not with obesity. The preproghrelin Met72 carrier status seems to be protective against fat accumulation and associated metabolic comorbidities.
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| 8. |
- Zurauskiene, N., et al.
(författare)
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Semiconductor nanostructures for infrared applications
- 2004
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Ingår i: Functional Nanomaterials For Optoelectronics And Other Applications. - : Trans Tech Publications Inc.. ; , s. 99-108
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Konferensbidrag (refereegranskat)abstract
- The results of time-resolved photo luminescence (TRPL) and optically detected microwave resonance (ODMR) spectroscopy investigations of semiconductor quantum dots and quantum wells are presented. The ODMR spectra of InAs/GaAs QDs were detected via modulation of the total intensity of the QDs emission induced by 95 GHz microwave excitation and the exciton fine structure was studied. Very long life times (up to 10 ns) of photoexcited carriers were observed in this system using TRPL at low temperatures and excitation intensities promising higher responsitivity of such QDs for infrared photodetector development. The effects of proton and alpha particles irradiation on carrier dynamics were investigated on different InGaAs/GaAs, InAlAs/AlGaAs and GaAs/AlGaAs QD and QW systems. The results showed that carrier lifetimes in QDs are much less affected by proton irradiation than that in QWs. A strong influence of irradiation on PL intensity was observed in multiple QWs after high-energy alpha particles irradiation.
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| 9. |
- Castillo Leon, Jaime, et al.
(författare)
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Purification and substrate specificity of peroxidase from sweet potato tubers
- 2002
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Ingår i: Plant Science. - 0168-9452. ; 163:5, s. 1011-1019
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Tidskriftsartikel (refereegranskat)abstract
- Previously the screening of tropical plants demonstrated a high peroxidase activity in sweet potato (Ipomoea batatas) tubers. The major peroxidase pool is localized in peel. Using peel of sweet potato as a source, the sweet potato peroxidase (SPP) has been isolated and purified to homogeneity. The enzyme purification included homogenization, extraction of colored compounds and consecutive chromatographies on Phenyl-Sepharose and DEAE-Toyopearl. The purified SPP had specific activity of 4900 U mg(-1) protein, RZ (ratio of absorbances at 403 and 280 nm, respectively) 3.4, molecular mass of 37 kDa and isoelectric point of 3.5. The spectrum of peroxidase from sweet potato is typical for plant peroxidases with a Soret maximum at 401 nm and the maxima in the visible region at 497 and 638 nm, respectively. The substrate specificity of SPP is distinct from the specificity of other plant peroxidases, ferulic acid being the best substrate for SPP.
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| 10. |
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