TY  - JOUR
A1  - Bakirci, Ezgi
A1  - Frank, Andreas
A1  - Gumbel, Simon
A1  - Otto, Paul F.
A1  - Fürsattel, Eva
A1  - Tessmer, Ingrid
A1  - Schmidt, Hans‐Werner
A1  - Dalton, Paul D.
T1  - Melt Electrowriting of Amphiphilic Physically Crosslinked Segmented Copolymers
JF  - Macromolecular Chemistry and Physics
N2  - Various (AB)\(_{n}\) and (ABAC)\(_{n}\) segmented copolymers with hydrophilic and hydrophobic segments are processed via melt electrowriting (MEW). Two different (AB)\(_{n}\) segmented copolymers composed of bisurea segments and hydrophobic poly(dimethyl siloxane) (PDMS) or hydrophilic poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEG-PPO) segments, while the amphiphilic (ABAC)\(_{n}\) segmented copolymers consist of bisurea segments in the combination of hydrophobic PDMS segments and hydrophilic PPO-PEG-PPO segments with different ratios, are explored. All copolymer compositions are processed using the same conditions, including nozzle temperature, applied voltage, and collector distance, while changes in applied pressure and collector speed altered the fiber diameter in the range of 7 and 60 µm. All copolymers showed excellent processability with MEW, well-controlled fiber stacking, and inter-layer bonding. Notably, the surfaces of all four copolymer fibers are very smooth when visualized using scanning electron microscopy. However, the fibers show different roughness demonstrated with atomic force microscopy. The non-cytotoxic copolymers increased L929 fibroblast attachment with increasing PDMS content while the different copolymer compositions result in a spectrum of physical properties.
KW  - melt electrowriting
KW  - 3D printing
KW  - additive manufacturing
KW  - electrohydrodynamics
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257572
VL  - 222
IS  - 22
ER  - 
TY  - JOUR
A1  - Buechner, Claudia N.
A1  - Maiti, Atanu
A1  - Drohat, Alexander C.
A1  - Tessmer, Ingrid
T1  - Lesion search and recognition by thymine DNA glycosylase revealed by single molecule imaging
JF  - Nucleic Acids Research
N2  - The ability of DNA glycosylases to rapidly and efficiently detect lesions among a vast excess of nondamaged DNA bases is vitally important in base excision repair (BER). Here, we use singlemolecule imaging by atomic force microscopy (AFM) supported by a 2-aminopurine fluorescence base flipping assay to study damage search by human thymine DNA glycosylase (hTDG), which initiates BER of mutagenic and cytotoxic G:T and G:U mispairs in DNA. Our data reveal an equilibrium between two conformational states of hTDG-DNA complexes, assigned as search complex (SC) and interrogation complex (IC), both at target lesions and undamaged DNA sites. Notably, for both hTDG and a second glycosylase, hOGG1, which recognizes structurally different 8-oxoguanine lesions, the conformation of the DNA in the SC mirrors innate structural properties of their respective target sites. In the IC, the DNA is sharply bent, as seen in crystal structures of hTDG lesion recognition complexes, which likely supports the base flipping required for lesion identification. Our results support a potentially general concept of sculpting of glycosylases to their targets, allowing them to exploit the energetic cost of DNA bending for initial lesion sensing, coupled with continuous (extrahelical) base interrogation during lesion search by DNA glycosylases.
KW  - Escherichia coli AlkA
KW  - undamaged DNA
KW  - substrate recognition
KW  - intrahelical lesion
KW  - uracil binding
KW  - structural basis
KW  - mismatch recognition
KW  - damaged DNA
KW  - base excision repair
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148795
VL  - 43
IS  - 5
ER  - 
TY  - JOUR
A1  - Tessmer, Ingrid
A1  - Kaur, Parminder
A1  - Lin, Jiangguo
A1  - Wang, Hong
T1  - Investigating bioconjugation by atomic force microscopy
JF  - Journal of Nanobiotechnology
N2  - Nanotechnological applications increasingly exploit the selectivity and processivity of biological molecules. Integration of biomolecules such as proteins or DNA into nano-systems typically requires their conjugation to surfaces, for example of carbon-nanotubes or fluorescent quantum dots. The bioconjugated nanostructures exploit the unique strengths of both their biological and nanoparticle components and are used in diverse, future oriented research areas ranging from nanoelectronics to biosensing and nanomedicine. Atomic force microscopy imaging provides valuable, direct insight for the evaluation of different conjugation approaches at the level of the individual molecules. Recent technical advances have enabled high speed imaging by AFM supporting time resolutions sufficient to follow conformational changes of intricately assembled nanostructures in solution. In addition, integration of AFM with different spectroscopic and imaging approaches provides an enhanced level of information on the investigated sample. Furthermore, the AFM itself can serve as an active tool for the assembly of nanostructures based on bioconjugation. AFM is hence a major workhorse in nanotechnology; it is a powerful tool for the structural investigation of bioconjugation and bioconjugation-induced effects as well as the simultaneous active assembly and analysis of bioconjugation-based nanostructures.
KW  - nanorobot
KW  - biosensors
KW  - nanomedicine
KW  - nanolithography
KW  - nanoelectronics
KW  - bioconjugation
KW  - nanotechnology
KW  - atomic force microscopy (AFM)
KW  - DNA origami
KW  - single molecule
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-129477
VL  - 11
IS  - 25
ER  - 
TY  - JOUR
A1  - Szambowska, Anna
A1  - Tessmer, Ingrid
A1  - Kursula, Petri
A1  - Usskilat, Christian
A1  - Prus, Potr
A1  - Pospiech, Helmut
A1  - Grosse, Frank
T1  - DNA binding properties of human Cdc45 suggest a function as molecular wedge for DNA unwinding
JF  - Nucleic Acids Research
N2  - The cell division cycle protein 45 (Cdc45) represents an essential replication factor that, together with the Mcm2-7 complex and the four subunits of GINS, forms the replicative DNA helicase in eukaryotes. Recombinant human Cdc45 (hCdc45) was structurally characterized and its DNA-binding properties were determined. Synchrotron radiation circular dichroism spectroscopy, dynamic light scattering, small-angle X-ray scattering and atomic force microscopy revealed that hCdc45 exists as an alpha-helical monomer and possesses a structure similar to its bacterial homolog RecJ. hCdc45 bound long (113-mer or 80-mer) single-stranded DNA fragments with a higher affinity than shorter ones (34-mer). hCdc45 displayed a preference for 3' protruding strands and bound tightly to single-strand/double-strand DNA junctions, such as those presented by Y-shaped DNA, bubbles and displacement loops, all of which appear transiently during the initiation of DNA replication. Collectively, our findings suggest that hCdc45 not only binds to but also slides on DNA with a 3'-5' polarity and, thereby acts as a molecular 'wedge' to initiate DNA strand displacement.
KW  - protein secondary structure
KW  - circular dichroism spectra
KW  - small-angle scattering
KW  - single-stranded-DNA
KW  - cyclin-dependent kinases
KW  - ray solution scattering
KW  - saccharmyces cerevisiae
KW  - escherichia coli
KW  - recj exonuclease
KW  - s-phase
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-117538
SN  - 1362-4962
VL  - 42
IS  - 4
ER  - 
TY  - JOUR
A1  - Tessmer, Ingrid
A1  - Melikishvili, Manana
A1  - Fried, Michael G.
T1  - Cooperative cluster formation, DNA bending and base-flipping by O\(^6\)-alkylguanine-DNA alkyltransferase
JF  - Nucleic Acids Research
N2  - O\(^6\)-Alkylguanine-DNA alkyltransferase (AGT) repairs mutagenic O\(^6\)-alkylguanine and O\(^4\)-alkylthymine adducts in DNA, protecting the genome and also contributing to the resistance of tumors to chemotherapeutic alkylating agents. AGT binds DNA cooperatively, and cooperative interactions are likely to be important in lesion search and repair. We examined morphologies of complexes on long, unmodified DNAs, using analytical ultracentrifugation and atomic force microscopy. AGT formed clusters of 11 proteins. Longer clusters, predicted by the McGhee-von Hippel model, were not seen even at high [protein]. Interestingly, torsional stress due to DNA unwinding has the potential to limit cluster size to the observed range. DNA at cluster sites showed bend angles (similar to 0, similar to 30 and similar to 60 degrees) that are consistent with models in which each protein induces a bend of similar to 30 degrees. Distributions of complexes along the DNA are incompatible with sequence specificity but suggest modest preference for DNA ends. These properties tell us about environments in which AGT may function. Small cooperative clusters and the ability to accommodate a range of DNA bends allow function where DNA topology is constrained, such as near DNA-replication complexes. The low sequence specificity allows efficient and unbiased lesion search across the entire genome.
KW  - inactivation
KW  - nucleotide excision-repair
KW  - atomic-force microscopy
KW  - noncooperative binding
KW  - restricition enzymes
KW  - complex stability
KW  - stranded DNAs
KW  - protein
KW  - chemotherapy
KW  - AGT
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-133949
VL  - 40
IS  - 17
ER  - 
TY  - JOUR
A1  - Bangalore, Disha M.
A1  - Heil, Hannah S.
A1  - Mehringer, Christian F.
A1  - Hirsch, Lisa
A1  - Hemmen, Katharina
A1  - Heinze, Katrin G.
A1  - Tessmer, Ingrid
T1  - Automated AFM analysis of DNA bending reveals initial lesion sensing strategies of DNA glycosylases
JF  - Scientific Reports
N2  - Base excision repair is the dominant DNA repair pathway of chemical modifications such as deamination, oxidation, or alkylation of DNA bases, which endanger genome integrity due to their high mutagenic potential. Detection and excision of these base lesions is achieved by DNA glycosylases. To investigate the remarkably high efficiency in target site search and recognition by these enzymes, we applied single molecule atomic force microscopy (AFM) imaging to a range of glycosylases with structurally different target lesions. Using a novel, automated, unbiased, high-throughput analysis approach, we were able to resolve subtly different conformational states of these glycosylases during DNA lesion search. Our results lend support to a model of enhanced lesion search efficiency through initial lesion detection based on altered mechanical properties at lesions. Furthermore, its enhanced sensitivity and easy applicability also to other systems recommend our novel analysis tool for investigations of diverse, fundamental biological interactions.
KW  - atomic-force microscopy
KW  - base pairs
KW  - molecular structure
KW  - crystal structure
KW  - structural basis
KW  - repair
KW  - recognition
KW  - 8-oxoguanine
KW  - thymine
KW  - mismatches
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-231338
VL  - 10
ER  - 
TY  - JOUR
A1  - Zaho, Huaying
A1  - Ghirlando, Rodolfo
A1  - Alfonso, Carlos
A1  - Arisaka, Fumio
A1  - Attali, Ilan
A1  - Bain, David L.
A1  - Bakhtina, Marina M.
A1  - Becker, Donald F.
A1  - Bedwell, Gregory J.
A1  - Bekdemir, Ahmet
A1  - Besong, Tabot M. D.
A1  - Birck, Catherine
A1  - Brautigam, Chad A.
A1  - Brennerman, William
A1  - Byron, Olwyn
A1  - Bzowska, Agnieszka
A1  - Chaires, Jonathan B.
A1  - Chaton, Catherine T.
A1  - Coelfen, Helmbut
A1  - Connaghan, Keith D.
A1  - Crowley, Kimberly A.
A1  - Curth, Ute
A1  - Daviter, Tina
A1  - Dean, William L.
A1  - Diez, Ana I.
A1  - Ebel, Christine
A1  - Eckert, Debra M.
A1  - Eisele, Leslie E.
A1  - Eisenstein, Edward
A1  - England, Patrick
A1  - Escalante, Carlos
A1  - Fagan, Jeffrey A.
A1  - Fairman, Robert
A1  - Finn, Ron M.
A1  - Fischle, Wolfgang
A1  - Garcia de la Torre, Jose
A1  - Gor, Jayesh
A1  - Gustafsson, Henning
A1  - Hall, Damien
A1  - Harding, Stephen E.
A1  - Hernandez Cifre, Jose G.
A1  - Herr, Andrew B.
A1  - Howell, Elizabeth E.
A1  - Isaac, Richard S.
A1  - Jao, Shu-Chuan
A1  - Jose, Davis
A1  - Kim, Soon-Jong
A1  - Kokona, Bashkim
A1  - Kornblatt, Jack A.
A1  - Kosek, Dalibor
A1  - Krayukhina, Elena
A1  - Krzizike, Daniel
A1  - Kusznir, Eric A.
A1  - Kwon, Hyewon
A1  - Larson, Adam
A1  - Laue, Thomas M.
A1  - Le Roy, Aline
A1  - Leech, Andrew P.
A1  - Lilie, Hauke
A1  - Luger, Karolin
A1  - Luque-Ortega, Juan R.
A1  - Ma, Jia
A1  - May, Carrie A.
A1  - Maynard, Ernest L.
A1  - Modrak-Wojcik, Anna
A1  - Mok, Yee-Foong
A1  - Mücke, Norbert
A1  - Nagel-Steger, Luitgard
A1  - Narlikar, Geeta J.
A1  - Noda, Masanori
A1  - Nourse, Amanda
A1  - Obsil, Thomas
A1  - Park, Chad K
A1  - Park, Jin-Ku
A1  - Pawelek, Peter D.
A1  - Perdue, Erby E.
A1  - Perkins, Stephen J.
A1  - Perugini, Matthew A.
A1  - Peterson, Craig L.
A1  - Peverelli, Martin G.
A1  - Piszczek, Grzegorz
A1  - Prag, Gali
A1  - Prevelige, Peter E.
A1  - Raynal, Bertrand D. E.
A1  - Rezabkova, Lenka
A1  - Richter, Klaus
A1  - Ringel, Alison E.
A1  - Rosenberg, Rose
A1  - Rowe, Arthur J.
A1  - Rufer, Arne C.
A1  - Scott, David J.
A1  - Seravalli, Javier G.
A1  - Solovyova, Alexandra S.
A1  - Song, Renjie
A1  - Staunton, David
A1  - Stoddard, Caitlin
A1  - Stott, Katherine
A1  - Strauss, Holder M.
A1  - Streicher, Werner W.
A1  - Sumida, John P.
A1  - Swygert, Sarah G.
A1  - Szczepanowski, Roman H.
A1  - Tessmer, Ingrid
A1  - Toth, Ronald T.
A1  - Tripathy, Ashutosh
A1  - Uchiyama, Susumu
A1  - Uebel, Stephan F. W.
A1  - Unzai, Satoru
A1  - Gruber, Anna Vitlin
A1  - von Hippel, Peter H.
A1  - Wandrey, Christine
A1  - Wang, Szu-Huan
A1  - Weitzel, Steven E
A1  - Wielgus-Kutrowska, Beata
A1  - Wolberger, Cynthia
A1  - Wolff, Martin
A1  - Wright, Edward
A1  - Wu, Yu-Sung
A1  - Wubben, Jacinta M.
A1  - Schuck, Peter
T1  - A Multilaboratory Comparison of Calibration Accuracy and the Performance of External References in Analytical Ultracentrifugation
JF  - PLoS ONE
N2  - Analytical ultracentrifugation (AUC) is a first principles based method to determine absolute sedimentation coefficients and buoyant molar masses of macromolecules and their complexes, reporting on their size and shape in free solution. The purpose of this multi-laboratory study was to establish the precision and accuracy of basic data dimensions in AUC and validate previously proposed calibration techniques. Three kits of AUC cell assemblies containing radial and temperature calibration tools and a bovine serum albumin (BSA) reference sample were shared among 67 laboratories, generating 129 comprehensive data sets. These allowed for an assessment of many parameters of instrument performance, including accuracy of the reported scan time after the start of centrifugation, the accuracy of the temperature calibration, and the accuracy of the radial magnification. The range of sedimentation coefficients obtained for BSA monomer in different instruments and using different optical systems was from 3.655 S to 4.949 S, with a mean and standard deviation of (4.304\(\pm\)0.188) S (4.4%). After the combined application of correction factors derived from the external calibration references for elapsed time, scan velocity, temperature, and radial magnification, the range of s-values was reduced 7-fold with a mean of 4.325 S and a 6-fold reduced standard deviation of \(\pm\)0.030 S (0.7%). In addition, the large data set provided an opportunity to determine the instrument-to-instrument variation of the absolute radial positions reported in the scan files, the precision of photometric or refractometric signal magnitudes, and the precision of the calculated apparent molar mass of BSA monomer and the fraction of BSA dimers. These results highlight the necessity and effectiveness of independent calibration of basic AUC data dimensions for reliable quantitative studies.
KW  - fluorescence-detected sedimentation
KW  - size exclusion chromatography
KW  - field flow fractionation
KW  - spinco ultracentrifuge
KW  - aggregation
KW  - bead models
KW  - velocity
KW  - hydrodynamics
KW  - biopharmaceuticals
KW  - proteins
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-151903
VL  - 10
IS  - 5
ER  -