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Lingyun Zhu

Publications and source records attributed to Lingyun Zhu.

14 recordsLinked to original sources
PubMed2007

Two-photon absorption properties of iron(II) and ruthenium(II) trischelate complexes of 2,2':4,4' ':4',4' ''-quaterpyridinium ligands.

A series of RuII or FeII trischelate complex salts containing N-methyl/aryl-2,2':4,4' ':4',4' ''-quaterpyridinium ligands that has previously been subjected to quadratic nonlinear optical studies (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 13399) has now been investigated for two-photon absorbing behavior. Z-scan measurements using a 750 nm laser afford reasonably large two-photon absorption (2PA) cross-sections sigma2 of ca. 62-180 GM for the RuII complexes, but only very weak 2PA is observed for the FeII compounds. The excited-state and 2PA properties of the representative chromophore [RuII(Me2Qpy2+)3]8+ (Me2Qpy2+=N' ',N' ''-dimethyl-2,2':4,4' ':4',4' ''-quaterpyridinium) have also been investigated by using semiempirical intermediate neglect of differential overlap/multireference-determinant single and double configuration interaction computations with the optimized geometry obtained via density functional theory. The calculated sigma2 value of ca. 624 GM at 1.70 eV for this metal-to-ligand charge-transfer chromophore is about 10 times larger than that obtained from the Z-scan studies.

Journal Article↗
PubMed2006

Singlet-triplet splittings and their relevance to the spin-dependent exciton formation in light-emitting polymers: an EOM/CCSD study.

By employing the coupled-cluster equation of motion method (EOM/CCSD) for excited-state structures, we have investigated the structure dependence of the singlet and triplet exciton splittings, through extensive calculations for polythiophene (PT), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(thienylenevinylene) (PTV), polyparaphenylene vinylene (PPV), MEHPPV, polyparaphenylene ethylene (PPE), polyfluorene (PFO), and ladder-type polyparaphenylene (mLPPP). The results for the polymer are extrapolated through computations for the oligomers with increasing length. Recent investigations have been quite controversial about whether the internal quantum efficiency of electroluminescence could be higher than the 25% spin statistics limit or not in polymeric materials. Using a simple relationship between the exciton formation rate and the excitation energy level, we have discussed the material-dependent ratios of singlet and triplet exciton formation, which are in good agreement with the magnetic-field resonance detected transient spectroscopy measurement by Wohlgenannt et al. for a series of electronic polymers. This provides another piece of evidence to support the view that the internal quantum efficiency for conjugated polymers can exceed the 25% limit.

Journal Article↗
PubMed2006

The correction vector method for three-photon absorption: the effects of pi conjugation in extended rylenebis(dicarboximide)s.

A correction vector method within the multireference determinant single and double configuration interaction approximation coupled with the semiempirical intermediate neglect of differential overlap Hamiltonian has been developed for the computation of single and multiphoton absorption spectra of conjugated molecules. We study the effect of pi conjugation on these properties in the extended rylenebis(dicarboximide)s. The one-, two-, and three-photon absorption cross sections of the lowest-lying excited states show a power law dependence on the conjugation length, with exponents of about 1.3, 2.6, and 5.6, respectively. The maximum value of the three-photon absorption cross section in these molecules is calculated to be 1.06x10(-78) cm6 s2photon2 for photon energy at 0.57 eV.

Journal Article↗
PubMed2006

Structure-property relationships for three-photon absorption in stilbene-based dipolar and quadrupolar chromophores.

Based on essential-state models for three-photon absorption (3PA), we have investigated the structure-property relationships for stilbene-based dipolar and quadrupolar chromophores. The emphasis lies on the evolution of the 3PA cross section with the degree of ground-state polarization. For dipolar systems, we find a dominant role played by Deltamu, which expresses the change in dipole moment between the ground state and the 3PA active excited state. Thus, the strategies usually applied to maximize the second-order polarizability beta are also applicable to optimize the 3PA cross section. For quadrupolar systems, the 3PA response is dominated by contributions from channels including various low-lying two-photon allowed states, which limits the applicability of essential-state models. Optimization strategies can be proposed but vary for different ranges of ground-state polarization.

Journal Article↗
PubMed2006

Noninvasive bioluminescence imaging of normal and spontaneously transformed prostate tissue in mice.

Several transgenic mouse models of prostate cancer have been developed recently that are able to recapitulate many key biological features of the human condition. It would, therefore, be desirable to employ these models to test the efficacy of new therapeutics before clinical trial; however, the variable onset and non-visible nature of prostate tumor development limit their use for such applications. We now report the generation of a transgenic reporter mouse that should obviate these limitations by enabling noninvasive in vivo bioluminescence imaging of normal and spontaneously transformed prostate tissue in the mouse. We used an 11-kb fragment of the human prostate-specific antigen (PSA) promoter to achieve specific and robust expression of firefly luciferase in the prostate glands of transgenic mice. Ex vivo bioluminescence imaging and in situ hybridization analysis confirmed that luciferase expression was restricted to the epithelium in all four lobes of the prostate. We also show that PSA-Luc mice exhibit decreased but readily detectable levels of in vivo bioluminescence over extended time periods following androgen ablation. These results suggest that this reporter should enable in vivo imaging of both androgen-dependent and androgen-independent prostate tumor models. As proof-of-principle, we show that we could noninvasively image SV40 T antigen-induced prostate tumorigenesis in mice with PSA-Luc. Furthermore, we show that our noninvasive imaging strategy can be successfully used to image tumor response to androgen ablation in transgenic mice and, as a result, that we can rapidly identify individual animals capable of sustaining tumor growth in the absence of androgen.

Androgens↗
PubMed2006

Binaphthalene molecules with tetrathiafulvalene units: CD spectrum modulation and new chiral molecular switches by reversible oxidation and reduction of tetrathiafulvalene units.

By combining the features of binaphthalene and tetrathiafulvalene (TTF), compounds 1-4 were designed for studies of chiral molecular switches. Absorption and CD spectral studies clearly indicate that the CD spectra resulting from axial chiral binaphthalene units can be modulated through the redox reactions of TTF units, which means new chiral molecular switches can be established on the basis of binaphthalene molecules with TTF units. The reference compound 5, which has one TTF unit rather than two as in the case of compounds 1, 3, and 4, failed to show such property, hinting that the presence of two or more TTF units is required for the realization of CD spectrum modulation. In addition, the manner of the CD spectrum modulation has been found to be dependent on the way TTF units are linked to the binaphthalene skeleton, in terms of the linker length, the positions for substitution, and the number of TTF units.

Journal Article↗
PubMed2005

Regulation of IkappaBalpha expression involves both NF-kappaB and the MAP kinase signaling pathways.

IkappaBalpha is an inhibitor of the nuclear transcription factor NF-kappaB. Binding of IkappaBalpha to NF-kappaB inactivates the transcriptional activity of NF-kappaB. Expression of IkappaBalpha itself is regulated by NF-kappaB, which provides auto-regulation of this signaling pathway. Here we present a mouse model for monitoring in vivo IkappaBalpha expression by imaging IkappaBalpha-luc transgenic mice for IkappaBalpha promoter driven luciferase activity. We demonstrated a rapid and systemic induction of IkappaBalpha expression in the transgenic mice following treatment with LPS. The induction was high in liver, spleen, lung and intestine and lower in the kidney, heart and brain. The luciferase induction in the liver correlated with increased IkappaBalpha mRNA level. Pre-treatment with proteasome inhibitor bortezomib dramatically suppressed LPS-induced luciferase activity. The p38 kinase inhibitor SB203580 also showed moderate inhibition of LPS-induced luciferase activity. Analysis of IkappaBalpha mRNA in the liver tissue showed a surprising increase of the IkappaBalpha mRNA after bortezomib and SB203580 treatments, which could be due to increased IkappaBalpha mRNA stability. Our data demonstrate that regulation of IkappaBalpha expression involves both the NF-kappaB and the p38 signaling pathways. The IkappaBalpha-luc transgenic mice are useful for analyzing IkappaBalpha expression and the NF-kappaB transcriptional activity in vivo.

Journal Article↗
PubMed2004

Three-photon absorption in anthracene-porphyrin-anthracene triads: a quantum-chemical study.

We have applied correlated quantum-chemical methods to investigate the three-photon absorption (3PA) response of a porphyrin triad derivative, where the central macrocycle is linked in mesopositions to two anthracene units via acetylenic bridges. The 3PA frequency-dependent spectrum of this derivative is dominated by a single resonance feature in the transparent region, associated with charge-transfer states between porphyrin and anthracene. The calculations indicate a two order of magnitude enhancement in the 3PA cross section in the triad molecule with respect to the individual entities, which is attributed to close one-, two-, and three-photon resonances together with strong electronic couplings among the units.

Journal Article↗
PubMed2004

Non-invasive imaging of GFAP expression after neuronal damage in mice.

Up-regulation of glial fibrillary acidic protein (GFAP) expression is often used as a surrogate marker of neuronal damage. We have created a transgenic mouse line that carries the luciferase gene under the transcriptional control of the mouse GFAP promoter. Biophotonic imaging was used to non-invasively detect the increase in GFAP expression after kainic acid induced neuronal cell death. We demonstrate that after kainic acid treatment, strong biophotonic signals were detected from the brain area. This correlated with both endogenous GFAP and luciferase RNA levels as well as with hippocampal cell death observed histologically. The transgenic mouse line will provide a powerful tool to dynamically monitor neuronal cell death in the living animal and will aid in the discovery and development of drugs to treat damage due to stroke and other neurodegenerative diseases.

Animals↗
PubMed2003

Induction of apoptosis by the p53-related p73 and partial inhibition by the baculovirus-encoded p35 in neuronal cells.

To better understand whether the p53-related p73 gene could induce neuronal apoptosis, we tested whether p73 induced cell killing in three neuronal cell lines and whether apoptosis could be inhibited by p35, a baculovirus-encoded protein that blocks caspase 3. Recombinant adenoviruses carrying the hemagglutinin (HA)-tagged p73beta or p35, or the green fluorescent protein gene driven by the cytomegalovirus immediate-early promoter were constructed, and used to infect human SK-N-AS and SK-N-SH neuroblastoma, and rat PC12 pheochromocytoma cells. Infection with Adp73beta virus resulted in p73beta over-expression and substantial reduction of cell viability due to apoptosis in all three neuronal cell lines as compared with the control AdGFP virus. These results indicate that p73beta over-expression in neuronal cells could induce apoptotic cell death regardless of the endogenous expression of p73. The p73 effect was partially blocked by co-expression of the wild-type p35, suggesting caspase-mediated cell killing. Insertion of a hemagglutinin (HA) tag at the N-terminus of p35 markedly reduced its ability to inhibit the p73 effect compared with the wild-type p35, while insertion of an HA tag to the C-terminus of p35 had no appreciable effect. Taken together, our results suggest that the N-terminal structure of p35 is critical for its anti-apoptotic activity on p73-induced apoptosis in neuronal cells.

Adenoviridae↗
PubMed2003

[Introduction to medical data mining].

Modern medicine generates a great deal of information stored in the medical database. Extracting useful knowledge and providing scientific decision-making for the diagnosis and treatment of disease from the database increasingly becomes necessary. Data mining in medicine can deal with this problem. It can also improve the management level of hospital information and promote the development of telemedicine and community medicine. Because the medical information is characteristic of redundancy, multi-attribution, incompletion and closely related with time, medical data mining differs from other one. In this paper we have discussed the key techniques of medical data mining involving pretreatment of medical data, fusion of different pattern and resource, fast and robust mining algorithms and reliability of mining results. The methods and applications of medical data mining based on computation intelligence such as artificial neural network, fuzzy system, evolutionary algorithms, rough set, and support vector machine have been introduced. The features and problems in data mining are summarized in the last section.

Algorithms↗
PubMed2002

Multiple transcription initiation sites, alternative splicing, and differential polyadenylation contribute to the complexity of human neurofibromatosis 2 transcripts.

Northern blot analysis has shown that the human neurofibromatosis type 2 (NF2) cDNA hybridizes to multiple RNA species. To examine whether these hybridizing RNA species represent NF2 transcripts, we cloned the complete NF2 cDNA by a combination of techniques: 5' and 3' rapid amplification of cDNA ends, RT-PCR, and searching and sequencing the NF2-related cDNA clones from the IMAGE consortium. We showed that human NF2 transcripts initiate at multiple positions. Analogous to those reported previously, NF2 transcripts undergo alternative splicing in the coding exons. We isolated eight alternatively spliced NF2 cDNA isoforms, including one that contains a new exon termed exon 2', which potentially could encode proteins of different sizes. We assembled the overlapping cDNA fragments, and the longest NF2 cDNA, containing all 17 exons, consists of 6067 nucleotides, which is consistent with the size of the major RNA species hybridized to the NF2 probe. The cDNA has a 425-nucleotide 5' untranslated region upstream from the ATG start codon, and a long 3' untranslated region of 3869 nucleotides. We also isolated two shorter NF2 cDNAs that were terminated by different polyadenylation signal sequences, which indicates that differential usage of multiple polyadenylation sites also contributes to the complexity of human NF2 transcripts. By reference to the transcription initiation site mapped, we analyzed the 5' flanking sequence of the human NF2 gene. Transient transfection analysis in human 293 kidney, SK-N-AS neuroblastoma, and NT2/D1 teratocarcinoma cells with NF2 promoter-luciferase chimeric constructs revealed a core promoter region extending 400 base pairs from the major transcription initiation site. Although multiple regions are required for full promoter activity, a site-directed mutagenesis experiment identified a GC-rich sequence (position -58 to -46), which could be bound by transcription factor Sp1, as a positive cis-acting regulatory element. Cotransfection studies in Drosophila melanogaster SL2 cells showed that Sp1 could activate the NF2 promoter through the GC-rich sequence.

Alternative Splicing↗