Publications by authors named "Christina Bauer"

33 Publications

Do Only White or Asian Males Belong in Genius Organizations? How Academic Organizations' Fixed Theories of Excellence Help or Hinder Different Student Groups' Sense of Belonging.

Front Psychol 2021 12;12:631142. Epub 2021 Feb 12.

Department of Educational Science and Psychology, Freie Universität Berlin, Berlin, Germany.

High-profile organizations often emphasize fixed giftedness rather than malleable effort-based criteria as critical for excellent achievements. With giftedness being primarily associated with White or Asian males, such organizational implicit theories of excellence may shape individuals' sense of belonging depending on the extent to which they match the , i.e., the prototypical gifted person which is typically imagined to be a White or Asian male. Previous research has reported fixed excellence theories emphasizing giftedness (vs. malleable theories emphasizing effort) to impair the sense of belonging of females and negatively stereotyped ethnic minorities. We investigate the combined effects of gender and ethnicity. We predicted that, while individuals whose gender and ethnicity do not match the gifted prototype show a reduced sense of belonging in fixed organizations, White/Asian males who match the gifted prototype show the opposite effect, experiencing a sense of belonging in fixed (vs. malleable) organizations. In an experimental study ( = 663 students), we manipulated advertising material used by a highly selective academic institution in Germany and tested effects on students' belonging. Whereas the original material emphasized giftedness as essential for excelling (fixed excellence version), our manipulated version stressed effort (malleable version). As expected, females from stereotyped ethnic minority groups felt less belonging in the fixed (vs. malleable) organization, while White/Asian males anticipated stronger belonging in the fixed (vs. malleable) organization. Fixed views of excellence impair negatively stereotyped individuals' belonging but may even strengthen the belonging of prototypical academic elites.
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http://dx.doi.org/10.3389/fpsyg.2021.631142DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7907512PMC
February 2021

Tofacitinib in the Treatment of Crohn's-Like Disease of the Pouch.

Am J Gastroenterol 2020 12;115(12):2116-2117

Division of Gastroenterology and Hepatology, University of North Carolina, Chapel Hill, North Carolina.

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http://dx.doi.org/10.14309/ajg.0000000000000801DOI Listing
December 2020

Characteristics of Fecal Microbiota Transplantation Use in Inflammatory Bowel Disease Cohort.

Crohns Colitis 360 2020 Apr 18;2(2):otaa024. Epub 2020 Apr 18.

Division of Gastroenterology and Hepatology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.

Background: There is a growing interest in the role of gut bacteria in a number of diseases and an emerging hypothesis that inflammatory bowel disease (IBD) is triggered by microbial dysbiosis in genetically susceptible individuals. Currently, fecal microbiota transplantation (FMT) is utilized for the treatment of lostridium colitis. Data on the efficacy of FMT for IBD are mixed, but patients are interested in its use for the treatment of IBD. We sought to describe the use of FMT (self or medical professional administered) in individuals with IBD using IBD Partners, an Internet-based cohort.

Methods: Patients enrolled in the IBD Partners cohort were offered the opportunity to complete an optional survey on the use of FMT between January 2017 to September 2018 (n = 5430). A cross-sectional analysis was performed within patients who completed the survey and did not have a pouch or ostomy. Patients' demographic characteristics, disease activity and phenotype, mode of FMT delivery, and patient-reported efficacy were compared.

Results: Among 3274 eligible patients, 51 (1.6%) responded that they had an FMT in the past. Of patients undergoing FMT, 22 patients had the FMT for while 29 reported that the FMT was for another indication. Most patients receiving FMT for an indication other than had ulcerative colitis/indeterminate colitis (25, 86.2%). Colonoscopy (68.2%) and nasogastric tube (18.2%) were the most common routes of administration for patients receiving FMT for colitis. Self-administration (72.4%) and enemas (17.2%) were the most common routes of administration in patients receiving FMT for an alternate indication. Patients reporting FMT for an indication other than were less likely to have a physician directing their FMT treatment (20.6%) as compared to patients receiving FMT for (86.3%). Patient-reported efficacy was lower for FMT given for a non- indication.

Conclusions: Patients undergoing FMT for an indication other than infection were more likely to have ulcerative colitis, self-administer FMT, and were less likely to be receiving FMT under the guidance of a medical professional. FMT was not as effective for symptoms when given for a non- indication. Patients should be counseled on potential harms and lack of proven benefit associated with FMT for IBD indications to try to discourage self-administered FMT without proper medical oversite.
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http://dx.doi.org/10.1093/crocol/otaa024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7215656PMC
April 2020

Black and White Patients With Inflammatory Bowel Disease Show Similar Biologic Use Patterns With Medicaid Insurance.

Inflamm Bowel Dis 2021 Feb;27(3):364-370

Division of Gastroenterology and Hepatology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.

Background: Prior studies have identified racial disparities in the treatment and outcomes of inflammatory bowel disease (IBD). These disparities could be secondary to differences in biology, care delivery, or access to appropriate therapy. The primary aim of this study was to compare medication use among Medicaid-insured black and white patients with IBD, given uniform access to gastroenterologists and therapies.

Methods: We analyzed Medicaid Analytic eXtract data from 4 states (California, Georgia, North Carolina, and Texas) between 2006 and 2011. We compared the use of IBD-specific therapies, including analyses of postoperative therapy among patients with Crohn disease (CD). We performed bivariate analyses and multivariable logistic regression, adjusting for potential confounders.

Results: We identified 14,735 patients with IBD (4672 black [32%], 8277 with CD [58%]). In multivariable analysis, there was no significant difference in the odds of anti-tumor necrosis factor use by race for CD (adjusted odds ratio [aOR] = 1.13; 95% confidence interval [CI], 0.99-1.28] or ulcerative colitis (aOR = 1.12; 95% CI, 0.96-1.32). Black patients with CD were more likely than white patients to receive combination therapy (aOR = 1.50; 95% CI, 1.15-1.96), and black patients were more likely than white patients to receive immunomodulator monotherapy after surgery for CD (31% vs 18%; P = 0.004).

Conclusions: In patients with Medicaid insurance, where access to IBD-specific therapy should be similar for all individuals, there was no significant disparity by race in the utilization of IBD-specific therapies. Disparities in IBD treatment discussed in prior literature seem to be driven by socioeconomic or other issues affecting access to care.
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http://dx.doi.org/10.1093/ibd/izaa090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7885313PMC
February 2021

Systematic analysis of the binding behaviour of UHRF1 towards different methyl- and carboxylcytosine modification patterns at CpG dyads.

PLoS One 2020 21;15(2):e0229144. Epub 2020 Feb 21.

Center for Integrated Protein Science Munich at the TUM School of Life Sciences, Technische Universität München, Freising, Germany.

The multi-domain protein UHRF1 is essential for DNA methylation maintenance and binds DNA via a base-flipping mechanism with a preference for hemi-methylated CpG sites. We investigated its binding to hemi- and symmetrically modified DNA containing either 5-methylcytosine (mC), 5-hydroxymethylcytosine (hmC), 5-formylcytosine (fC), or 5-carboxylcytosine (caC). Our experimental results indicate that UHRF1 binds symmetrically carboxylated and hybrid methylated/carboxylated CpG dyads in addition to its previously reported substrates. Complementary molecular dynamics simulations provide a possible mechanistic explanation of how the protein could differentiate between modification patterns. First, we observe different local binding modes in the nucleotide binding pocket as well as the protein's NKR finger. Second, both DNA modification sites are coupled through key residues within the NKR finger, suggesting a communication pathway affecting protein-DNA binding for carboxylcytosine modifications. Our results suggest a possible additional function of the hemi-methylation reader UHRF1 through binding of carboxylated CpG sites. This opens the possibility of new biological roles of UHRF1 beyond DNA methylation maintenance and of oxidised methylcytosine derivates in epigenetic regulation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0229144PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7034832PMC
May 2020

A One-Step Process for the Construction of Phage Display scFv and VHH Libraries.

Mol Biotechnol 2020 Apr;62(4):228-239

Protein Engineering and Antibody Technologies, Merck Healthcare KGaA, Frankfurter Strasse 250, 64293, Darmstadt, Germany.

In this work we present a one-step cloning approach for the establishment of antibody phage display libraries relying on type IIs restriction enzymes. We show that single chain variable fragment (scFv) libraries with adequate qualities can readily be cloned in a 'scar-less' manner and that the isolation of antigen-specific antibodies from immunized chickens is feasible within three selection rounds. Moreover, we demonstrate the general applicability of this method by rapidly constructing and panning VHH single domain antibody phage display libraries from immunized Llama repertoires.
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http://dx.doi.org/10.1007/s12033-020-00236-0DOI Listing
April 2020

Response to Infliximab After Loss of Response to Adalimumab in Crohn's Disease.

Inflamm Bowel Dis 2020 01;26(2):e5

Division of Gastroenterology and Hepatology, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA.

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http://dx.doi.org/10.1093/ibd/izz286DOI Listing
January 2020

Correction: A convenient, bio-inspired approach to the synthesis of multi-functional, stable fluorescent silica nanoparticles using poly(ethylene-imine).

Nanoscale 2017 06;9(25):8889

Dept. of Chemistry, Whittier College, Whittier, CA 90608, USA.

Correction for 'A convenient, bio-inspired approach to the synthesis of multi-functional, stable fluorescent silica nanoparticles using poly(ethylene-imine)' by Christina A. Bauer, et al., Nanoscale, 2017, 9, 6509-6520.
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http://dx.doi.org/10.1039/c7nr90124kDOI Listing
June 2017

A convenient, bio-inspired approach to the synthesis of multi-functional, stable fluorescent silica nanoparticles using poly(ethylene-imine).

Nanoscale 2017 05;9(19):6509-6520

Dept. of Chemistry, Whittier College, Whittier, CA 90608, USA.

Branched poly(ethylene-imine) can be tagged with luminescent dyes (e.g., fluorescein isothiocyanate and tetramethylrhodamine isothiocyanate) and used to precipitate spherical silica particles from 10s-to-100s of nm diameter size under mild conditions. These dye-PEI/SiO nanoparticles are highly compatible with polar solvents to give bright fluorescent suspensions, and detailed photophysical characterization reveals well-separated dye moieties with an approximately homogeneous dispersion of dye-PEI conjugate throughout the SiO matrix. Reaction of PEI amine groups incorporated at the particle surface affords a simple method for post-synthesis functionalization of these materials, and the formation of FITC/Eosin-Y fluorescence resonance energy transfer pair-tagged particles and SiO@Au core-shell nanocomposites using this strategy is demonstrated. This bio-inspired approach to multi-functional SiO nanoparticles provides a range of potential advantages over traditional "inorganic" syntheses of similar materials, as it proceeds through a scalable, single-step reaction using inexpensive reagents, enables efficient incorporation of luminescent species into the resulting particles with very limited dye aggregation, and provides nanoparticles that do not require post-synthesis modification for further conjugation with species of interest. The method offers a simple means to generate complex nanocomposites, whereby a host of desired species can be incorporated both inside and on the surface of biocompatible SiO nanoparticles.
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http://dx.doi.org/10.1039/c7nr00462aDOI Listing
May 2017

Control of Grafting Density and Distribution in Graft Polymers by Living Ring-Opening Metathesis Copolymerization.

J Am Chem Soc 2017 03 3;139(10):3896-3903. Epub 2017 Mar 3.

Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.

Control over polymer sequence and architecture is crucial to both understanding structure-property relationships and designing functional materials. In pursuit of these goals, we developed a new synthetic approach that enables facile manipulation of the density and distribution of grafts in polymers via living ring-opening metathesis polymerization (ROMP). Discrete endo,exo-norbornenyl dialkylesters (dimethyl DME, diethyl DEE, di-n-butyl DBE) were strategically designed to copolymerize with a norbornene-functionalized polystyrene (PS), polylactide (PLA), or polydimethylsiloxane (PDMS) macromonomer mediated by the third-generation metathesis catalyst (G3). The small-molecule diesters act as diluents that increase the average distance between grafted side chains, generating polymers with variable grafting density. The grafting density (number of side chains/number of norbornene backbone repeats) could be straightforwardly controlled by the macromonomer/diluent feed ratio. To gain insight into the copolymer sequence and architecture, self-propagation and cross-propagation rate constants were determined according to a terminal copolymerization model. These kinetic analyses suggest that copolymerizing a macromonomer/diluent pair with evenly matched self-propagation rate constants favors randomly distributed side chains. As the disparity between macromonomer and diluent homopolymerization rates increases, the reactivity ratios depart from unity, leading to an increase in gradient tendency. To demonstrate the effectiveness of our method, an array of monodisperse polymers (PLA-ran-DME) bearing variable grafting densities (x = 1.0, 0.75, 0.5, 0.25) and total backbone degrees of polymerization (n = 167, 133, 100, 67, 33) were synthesized. The approach disclosed in this work therefore constitutes a powerful strategy for the synthesis of polymers spanning the linear-to-bottlebrush regimes with controlled grafting density and side chain distribution, molecular attributes that dictate micro- and macroscopic properties.
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http://dx.doi.org/10.1021/jacs.7b00791DOI Listing
March 2017

Phase-resolved pulse propagation through metallic photonic crystal slabs: plasmonic slow light.

Philos Trans A Math Phys Eng Sci 2017 Mar;375(2090)

4th Physics Institute, University of Stuttgart, Stuttgart, Germany

We characterized the electromagnetic field of ultra-short laser pulses after propagation through metallic photonic crystal structures featuring photonic and plasmonic resonances. The complete pulse information, i.e. the envelope and phase of the electromagnetic field, was measured using the technique of cross-correlation frequency resolved optical gating. In good agreement, measurements and scattering matrix simulations show a dispersive behaviour of the spectral phase at the position of the resonances. Asymmetric Fano-type resonances go along with asymmetric phase characteristics. Furthermore, the spectral phase is used to calculate the dispersion of the sample and possible applications in dispersion compensation are investigated. Group refractive indices of 700 and 70 and group delay dispersion values of 90 000 fs and 5000 fs are achieved in transverse electric and transverse magnetic polarization, respectively. The behaviour of extinction and spectral phase can be understood from an intuitive model using the complex transmission amplitude. An associated depiction in the complex plane is a useful approach in this context. This method promises to be valuable also in photonic crystal and filter design, for example, with regards to the symmetrization of the resonances.This article is part of the themed issue 'New horizons for nanophotonics'.
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http://dx.doi.org/10.1098/rsta.2016.0065DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5321827PMC
March 2017

Characterizing the Risk of False-Positive Hepatocellular Carcinoma in Recipients Transplanted With T2 MELD Exceptions.

Transplantation 2017 05;101(5):1099-1105

1 Division of Gastroenterology and Hepatology, University of Pennsylvania, Philadelphia, PA. 2 Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia, PA. 3 Division of Gastroenterology and Hepatology, University of North Carolina School of Medicine, Chapel Hill, NC.

Background: Patients with hepatocellular carcinoma (HCC) can receive Model for End-Stage Liver Disease (MELD) exception points to increase waitlist priority for liver transplantation. This process does not require a biopsy and is based on radiologic criteria. However, imaging modalities are imperfect, and some will ultimately have no HCC on explant.

Methods: This was a retrospective cohort study using national explant pathology data from 2012 to 2015. False-positive HCC was defined as answering "no" to the question: "was evidence of HCC (viable or nonviable) found in the explant?" in patients with T2 MELD exceptions.

Results: Four thousand one hundred seventeen patients received T2 MELD exceptions, of which 245 (6%) had false-positive HCC. Maximal tumor diameter of 3 to 5 cm and serum α fetoprotein (AFP) greater than 100 ng/mL at transplant yielded a 50% lower risk of false-positive HCC (odds ratio [OR], 0.45; 95% confidence interval [CI], 0.27-0.73 and OR, 0.57; 95% CI, 0.37-0.88, respectively). Recipients with immune-mediated liver disease were twice as likely to have no HCC on explant (OR, 2.12; 95% CI, 1.18-3.83) and had a predicted probability of false positive HCC greater than 10% regardless of largest tumor size or AFP. Significant among-center variability in the rate of false-positive HCC was seen.

Conclusions: The risk of false-positive HCC is markedly higher in certain groups, such that biopsy may be warranted before T2 MELD exception point approval. Transplant centers with high false-positive HCC rates may benefit from greater oversight.
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http://dx.doi.org/10.1097/TP.0000000000001660DOI Listing
May 2017

Praxis der Zukunft auf dem Supermarktdach.

Authors:
Christina Bauer

MMW Fortschr Med 2016 Dec;158(21-22):44

.

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http://dx.doi.org/10.1007/s15006-016-9092-1DOI Listing
December 2016

[Not Available].

Authors:
Christina Bauer

MMW Fortschr Med 2016 09;158(16):34

.

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http://dx.doi.org/10.1007/s15006-016-8713-zDOI Listing
September 2016

[Not Available].

Authors:
Christina Bauer

MMW Fortschr Med 2016 08;158(14):28-9

.

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http://dx.doi.org/10.1007/s15006-016-8565-6DOI Listing
August 2016

[A city person becomes an enthusiastic rural physician].

Authors:
Christina Bauer

MMW Fortschr Med 2016 Mar;158(4):32

.

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http://dx.doi.org/10.1007/s15006-016-7866-0DOI Listing
March 2016

Hierarchical macroscopic fibrillar adhesives: in situ study of buckling and adhesion mechanisms on wavy substrates.

Bioinspir Biomim 2015 Oct 23;10(6):066002. Epub 2015 Oct 23.

INM-Leibniz Institute for New Materials, Campus D2 2, D-66123 Saarbrücken, Germany. Saarland University, Campus D2 2, D-66123 Saarbrücken, Germany.

Nature uses hierarchical fibrillar structures to mediate temporary adhesion to arbitrary substrates. Such structures provide high compliance such that the flat fibril tips can be better positioned with respect to asperities of a wavy rough substrate. We investigated the buckling and adhesion of hierarchically structured adhesives in contact with flat smooth, flat rough and wavy rough substrates. A macroscopic model for the structural adhesive was fabricated by molding polydimethylsiloxane into pillars of diameter in the range of 0.3-4.8 mm, with up to three different hierarchy levels. Both flat-ended and mushroom-shaped hierarchical samples buckled at preloads one quarter that of the single level structures. We explain this behavior by a change in the buckling mode; buckling leads to a loss of contact and diminishes adhesion. Our results indicate that hierarchical structures can have a strong influence on the degree of adhesion on both flat and wavy substrates. Strategies are discussed that achieve highly compliant substrates which adhere to rough substrates.
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http://dx.doi.org/10.1088/1748-3190/10/6/066002DOI Listing
October 2015

A modular open platform for systematic functional studies under physiological conditions.

Nucleic Acids Res 2015 Sep 24;43(17):e112. Epub 2015 May 24.

Ludwig Maximilians University Munich, Department of Biology II and Center for Integrated Protein Science Munich (CIPSM), Großhaderner Strasse 2, 82152 Planegg-Martinsried, Germany

Any profound comprehension of gene function requires detailed information about the subcellular localization, molecular interactions and spatio-temporal dynamics of gene products. We developed a multifunctional integrase (MIN) tag for rapid and versatile genome engineering that serves not only as a genetic entry site for the Bxb1 integrase but also as a novel epitope tag for standardized detection and precipitation. For the systematic study of epigenetic factors, including Dnmt1, Dnmt3a, Dnmt3b, Tet1, Tet2, Tet3 and Uhrf1, we generated MIN-tagged embryonic stem cell lines and created a toolbox of prefabricated modules that can be integrated via Bxb1-mediated recombination. We used these functional modules to study protein interactions and their spatio-temporal dynamics as well as gene expression and specific mutations during cellular differentiation and in response to external stimuli. Our genome engineering strategy provides a versatile open platform for efficient generation of multiple isogenic cell lines to study gene function under physiological conditions.
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http://dx.doi.org/10.1093/nar/gkv550DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4787826PMC
September 2015

Phosphorylation of TET proteins is regulated via O-GlcNAcylation by the O-linked N-acetylglucosamine transferase (OGT).

J Biol Chem 2015 Feb 7;290(8):4801-4812. Epub 2015 Jan 7.

Biocenter, Ludwig-Maximilians University Munich, 82152 Planegg-Martinsried,; Center for Integrated Protein Science Munich (CIPSM), 81377 München, Germany. Electronic address:

TET proteins oxidize 5-methylcytosine to 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxylcytosine and thus provide a possible means for active DNA demethylation in mammals. Although their catalytic mechanism is well characterized and the catalytic dioxygenase domain is highly conserved, the function of the regulatory regions (the N terminus and the low-complexity insert between the two parts of the dioxygenase domains) is only poorly understood. Here, we demonstrate that TET proteins are subject to a variety of post-translational modifications that mostly occur at these regulatory regions. We mapped TET modification sites at amino acid resolution and show for the first time that TET1, TET2, and TET3 are highly phosphorylated. The O-linked GlcNAc transferase, which we identified as a strong interactor with all three TET proteins, catalyzes the addition of a GlcNAc group to serine and threonine residues of TET proteins and thereby decreases both the number of phosphorylation sites and site occupancy. Interestingly, the different TET proteins display unique post-translational modification patterns, and some modifications occur in distinct combinations. In summary, our results provide a novel potential mechanism for TET protein regulation based on a dynamic interplay of phosphorylation and O-GlcNAcylation at the N terminus and the low-complexity insert region. Our data suggest strong cross-talk between the modification sites that could allow rapid adaption of TET protein localization, activity, or targeting due to changing environmental conditions as well as in response to external stimuli.
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http://dx.doi.org/10.1074/jbc.M114.605881DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4335217PMC
February 2015

TET-mediated oxidation of methylcytosine causes TDG or NEIL glycosylase dependent gene reactivation.

Nucleic Acids Res 2014 Jul 19;42(13):8592-604. Epub 2014 Jun 19.

Department of Biology II, Ludwig-Maximilians University Munich and Center for Integrated Protein Science Munich (CIPSM), 82152 Planegg-Martinsried, Germany

The discovery of hydroxymethyl-, formyl- and carboxylcytosine, generated through oxidation of methylcytosine by TET dioxygenases, raised the question how these modifications contribute to epigenetic regulation. As they are subjected to complex regulation in vivo, we dissected links to gene expression with in vitro modified reporter constructs. We used an Oct4 promoter-driven reporter gene and demonstrated that in vitro methylation causes gene silencing while subsequent oxidation with purified catalytic domain of TET1 leads to gene reactivation. To identify proteins involved in this pathway we screened for TET interacting factors and identified TDG, PARP1, XRCC1 and LIG3 that are involved in base-excision repair. Knockout and rescue experiments demonstrated that gene reactivation depended on the glycosylase TDG, but not MBD4, while NEIL1, 2 and 3 could partially rescue the loss of TDG. These results clearly show that oxidation of methylcytosine by TET dioxygenases and subsequent removal by TDG or NEIL glycosylases and the BER pathway results in reactivation of epigenetically silenced genes.
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http://dx.doi.org/10.1093/nar/gku552DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4117777PMC
July 2014

Homo- and heterometallic luminescent 2-D stilbene metal-organic frameworks.

Dalton Trans 2014 Feb;43(7):2925-35

Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095, USA.

Metal-organic frameworks (MOFs) can provide a matrix for the assembly of organic chromophores into well-defined geometries, allowing for tuning of the material properties and study of structure-property relationships. Here, we report on the effect of the coordinated metal ion on the luminescence properties of eight isostructural MOFs having the formula M(1)2M(2)L3(DMF)2 (M(1) = M(2) = Zn (1), Cd (2), Mn (3), Co (4); M(1) = Zn, M(2) = Cd (5), Mn (6), Co (7); M(1) = Co, M(2) = Mn (8); L = trans-4,4'-stilbene dicarboxylate), synthesized by reaction of the appropriate metal nitrate or mixtures of metal nitrates with LH2 in DMF. The crystal structures of 2, 3 and 5-8 were determined by X-ray diffraction to be composed of trinuclear metal clusters linked by stilbene dicarboxylate linkers in a paddlewheel geometry, extending to form a 2-D layered structure. In the mixed-metal cases, the larger metal ion was found to occupy the octahedral site in the cluster while the smaller ion occupies the tetrahedral positions, suggesting a selective, ligand-directed assembly process for the mixed-metal species. Variable temperature magnetic measurements for paramagnetic MOFs 3 and 6-8 were consistent with the site occupancies determined crystallographically, and indicated weak intra-cluster antiferromagnetic coupling for 3 and 8. Comparison between the crystal structures of 2, 3 and 5-8 and those reported for 1 and 4 in the literature reveal close resemblances between linker environments, with important intermolecular stilbene-stilbene geometries that are comparable in all cases. Interestingly, pale-colored 1-3 and 5-7 display very similar emission profiles upon excitation at λ(ex) = 350 nm, whereas dark-colored 4 and 8 do not exhibit detectable emission spectra. The bright, well-resolved luminescence of 1, 2 and 5 is ascribed to rigidification of the linker upon coordination to the d(10) metal ions, whereas the weaker emission observed for 3, 6 and 7 is presumably a result of quenching due to close proximity of the linker to one or more paramagnetic ions. Time-resolved measurements for 1, 2, 5 and 6 reveal biexponential emission decays, where the lifetime of the longer-lived state corresponds to observed variations in the nearest-neighbor cofacial stilbene-stilbene distances in their crystal structures. For 3, a monoexponential decay with shorter lifetime was determined, indicating significant paramagnetic quenching of its emissive state.
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http://dx.doi.org/10.1039/c3dt52939hDOI Listing
February 2014

Light harvesting enhancement in solar cells with quasicrystalline plasmonic structures.

Opt Express 2013 May;21 Suppl 3:A363-71

Solar cells are important in the area of renewable energies. Since it is expensive to produce solar-grade silicon [Electrochem. Soc. Interface 17, 30 (2008)], especially thin-film solar cells are interesting. However, the efficiency of such solar cells is low. Therefore, it is important to increase the efficiency. The group of Polman has shown that a periodic arrangement of metal particles is able to enhance the absorbance of light [Nano Lett. 11, 1760 (2011)]. However, a quasicrystalline arrangement of the metal particles is expected to enhance the light absorbance independent of the incident polar and azimuthal angles due to the more isotropic photonic bandstructure. In this paper, we compare the absorption enhancement of a quasiperiodic photonic crystal to that of a periodic photonic crystal. We indeed find that the absorption enhancement for the quasicrystalline arrangement shows such an isotropic behavior. This implies that the absorption efficiency of the solar cell is relatively constant during the course of the day as well as the year. This is particularly important with respect to power distribution, power storage requirements, and the stability of the electric grid upon massive use of renewable energy.
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http://dx.doi.org/10.1364/OE.21.00A363DOI Listing
May 2013

Interaction of HPV E6 oncoproteins with specific proteasomal subunits.

Virology 2013 Nov 17;446(1-2):389-96. Epub 2013 Sep 17.

International Centre for Genetic Engineering and Biotechnology, Padriciano 99, I-34149 Trieste, Italy.

The Human Papillomavirus E6 oncoproteins have the capacity to target several of their cellular interacting partners for proteasome mediated degradation, and recent proteomic analyses suggest a close involvement of E6 with the cellular proteasome machinery. In this study we have performed an extensive analysis of the capacity of different E6 oncoproteins to interact with specific proteasome components. We demonstrate that multiple subunits of the proteasome can be bound by different HPV E6 oncoproteins. Furthermore, whilst most of these interactions appear independent of the E6AP ubiquitin ligase, the association of E6 with the major ubiquitin-accepting proteasome subunit, S5a, does require the presence of E6AP. One consequence of the interaction between E6/E6AP and S5a is enhanced ubiquitination of this proteasome subunit. These results suggest a complex interplay between E6 and the proteasome, only some aspects of which are dependent upon the E6AP ubiquitin ligase.
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http://dx.doi.org/10.1016/j.virol.2013.08.016DOI Listing
November 2013

Dynamic readers for 5-(hydroxy)methylcytosine and its oxidized derivatives.

Cell 2013 Feb 21;152(5):1146-59. Epub 2013 Feb 21.

Department of Molecular Cancer Research, Proteomics and Chromatin Biology, UMC Utrecht, 3584 CG Utrecht, the Netherlands.

Tet proteins oxidize 5-methylcytosine (mC) to generate 5-hydroxymethyl (hmC), 5-formyl (fC), and 5-carboxylcytosine (caC). The exact function of these oxidative cytosine bases remains elusive. We applied quantitative mass-spectrometry-based proteomics to identify readers for mC and hmC in mouse embryonic stem cells (mESC), neuronal progenitor cells (NPC), and adult mouse brain tissue. Readers for these modifications are only partially overlapping, and some readers, such as Rfx proteins, display strong specificity. Interactions are dynamic during differentiation, as for example evidenced by the mESC-specific binding of Klf4 to mC and the NPC-specific binding of Uhrf2 to hmC, suggesting specific biological roles for mC and hmC. Oxidized derivatives of mC recruit distinct transcription regulators as well as a large number of DNA repair proteins in mouse ES cells, implicating the DNA damage response as a major player in active DNA demethylation.
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http://dx.doi.org/10.1016/j.cell.2013.02.004DOI Listing
February 2013

2D quasiperiodic plasmonic crystals.

Sci Rep 2012 3;2:681. Epub 2012 Dec 3.

4 Physics Institute and Research Center SCoPE, University of Stuttgart , 70550 Stuttgart, Germany.

Nanophotonic structures with irregular symmetry, such as quasiperiodic plasmonic crystals, have gained an increasing amount of attention, in particular as potential candidates to enhance the absorption of solar cells in an angular insensitive fashion. To examine the photonic bandstructure of such systems that determines their optical properties, it is necessary to measure and model normal and oblique light interaction with plasmonic crystals. We determine the different propagation vectors and consider the interaction of all possible waveguide modes and particle plasmons in a 2D metallic photonic quasicrystal, in conjunction with the dispersion relations of a slab waveguide. Using a Fano model, we calculate the optical properties for normal and inclined light incidence. Comparing measurements of a quasiperiodic lattice to the modelled spectra for angle of incidence variation in both azimuthal and polar direction of the sample gives excellent agreement and confirms the predictive power of our model.
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http://dx.doi.org/10.1038/srep00681DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3512091PMC
May 2013

Prevalence and correlates of vitamin and supplement usage among men with a family history of prostate cancer.

Integr Cancer Ther 2012 Jun 5;11(2):83-9. Epub 2011 Aug 5.

Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109-0946, USA.

Hypotheses: Men who have a brother with prostate cancer have a 2-fold increased risk of being diagnosed with prostate cancer. Strategies employed by these men to reduce prostate cancer risk are not well understood. Preliminary studies have shown that men with a family history of prostate cancer have a high rate of vitamin and supplement usage aimed at the prevention of prostate cancer.

Study Design: The authors analyzed data from a cross-sectional study of men with familial and hereditary prostate cancer and their unaffected brothers. A total of 542 unaffected men who had at least one brother who had been diagnosed with prostate cancer regarding their use of vitamins and supplements, as well as the motivation for use, were interviewed.

Methods: The associations between subject characteristics and vitamin and supplement use were evaluated using an unconditional logistic regression modeling approach.

Results: Overall, 59.2% and 36.5% of men reported ever using and currently using, respectively, one or more vitamins or supplements (including multivitamins). One third of men took a vitamin or supplement that has been targeted for prostate health or cancer prevention, including green tea, magnesium, male hormones, saw palmetto, selenium, soy, vitamins A, C, E, and zinc. Increasing age at time of survey was associated with vitamin/supplement use (odds ratio [OR] = 1.03; 95% confidence interval [CI] = 1.01-1.05). After adjusting for age at time of survey, being younger than an affected brother was associated with vitamin and supplement use (OR = 1.51; 95% CI = 1.01-2.25). A total of 25% of men reported obtaining information from books or articles as the most common source of information.

Conclusions: The findings indicate that men at an increased risk for prostate cancer report a high rate of vitamin and supplement use, including supplements targeted for prostate cancer prevention. Men with a family history of prostate cancer represent a target population for future chemopreventative agents.
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http://dx.doi.org/10.1177/1534735411413262DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3213317PMC
June 2012

Hereditary prostate cancer as a feature of Lynch syndrome.

Fam Cancer 2011 Mar;10(1):37-42

Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, MI, USA.

Lynch Syndrome is an autosomal dominant condition characterized by early onset colorectal cancer (CRC) and is associated with cancers of the gastrointestinal and reproductive tracts. Germline mutations in DNA mismatch repair (MMR) genes have been causally associated with cancers of Lynch Syndrome. We investigated the occurrence of prostate cancer (PCa) in families with a history of colorectal cancer to assess prostate cancer as a feature of the Lynch Syndrome spectrum. Family pedigrees containing at least one CRC case as well as those meeting guidelines for Lynch Syndrome were identified and tumors were requested from participants who underwent radical prostatectomy (RP). Selected families were analyzed for association with type of PCa and clinical characteristics of aggressive disease. Microsatellite Instability (MSI) analysis was preformed on available tumors and correlated to loss of expression in MMR genes by immunohistochemical (IHC) staining. 95 individuals were identified as members of potential Lynch Syndrome families who underwent RP and 35 tumors from 31 families were received for MSI analysis. Two tumors from two unrelated families with known MMR mutations were MSI-high and one additional case from a third family was MSI-low. The remainder of the prostate cancer cases demonstrated no evidence of MSI. PCa incidence in families enriched for hereditary PCa with a history of Lynch Syndrome cancers is not strongly suggestive of the presence of an MMR mutation. However prostate tumors in known MMR mutation carriers did display MSI and loss of gene expression suggesting that PCa may arise in Lynch Syndrome due to defective DNA mismatch repair.
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http://dx.doi.org/10.1007/s10689-010-9388-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3089958PMC
March 2011

Diastereoselective heterogeneous bromination of stilbene in a porous metal-organic framework.

J Am Chem Soc 2009 Sep;131(35):12516-7

School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30032, USA.

Postsynthetic modification of a porous MOF, Zn(4)O(trans-4,4'-stilbene dicarboxylate)(3), with Br(2) results in diastereoselective bromination of the stilbene units. This is a heterogeneous process, with the stereocontrol originating in the rigidity of the coordinated ligand and the porous nature of the MOF, which allows "solution-like" access to reactive sites. X-ray diffraction and N(2) sorption studies suggest that partial bromination serves to increase the stability of this interpenetrated MOF structure.
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http://dx.doi.org/10.1021/ja900893pDOI Listing
September 2009

Influence of connectivity and porosity on ligand-based luminescence in zinc metal-organic frameworks.

J Am Chem Soc 2007 Jun 16;129(22):7136-44. Epub 2007 May 16.

Department of Nanoscale Science and Technology, and Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, USA.

Applications of metal-organic frameworks (MOFs) require close correlation between their structure and function. We describe the preparation and characterization of two zinc MOFs based on a flexible and emissive linker molecule, stilbene, which retains its luminescence within these solid materials. Reaction of trans-4,4'-stilbene dicarboxylic acid and zinc nitrate in N,N-dimethylformamide (DMF) yielded a dense 2-D network, 1, featuring zinc in both octahedral and tetrahedral coordination environments connected by trans-stilbene links. Similar reaction in N,N-diethylformamide (DEF) at higher temperatures resulted in a porous, 3-D framework structure, 2. This framework consists of two interpenetrating cubic lattices, each featuring basic zinc carboxylate vertices joined by trans-stilbene, analogous to the isoreticular MOF (IRMOF) series. We demonstrate that the optical properties of both 1 and 2 correlate with the local ligand environments observed in the crystal structures. Steady-state and time-resolved spectroscopic measurements reveal that the stilbene linkers in the dense structure 1 exhibit a small degree of interchromophore coupling. In contrast, the stilbenoid units in 2 display very little interaction in this low-density 3-D framework, with excitation and emission spectra characteristic of monomeric stilbenes, similar to the dicarboxylic acid in dilute solution. In both cases, the rigidity of the stilbene linker increases upon coordination to the inorganic units through inhibition of torsion about the central ethylene bond, resulting in luminescent crystals with increased emission lifetimes compared to solutions of trans-stilbene. The emission spectrum of 2 is found to depend on the nature of the incorporated solvent molecules, suggesting use of this or related materials in sensor applications.
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http://dx.doi.org/10.1021/ja0700395DOI Listing
June 2007

Silica particle formation in confined environments via bioinspired polyamine catalysis at near-neutral pH.

Small 2007 Jan;3(1):58-62

Nanoscale Science and Technology Department, Sandia National Laboratories, Livermore, CA 94551, USA.

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http://dx.doi.org/10.1002/smll.200600352DOI Listing
January 2007