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  1. Article ; Online: Imaging of Liposomes by Transmission Electron Microscopy.

    Baxa, Ulrich

    Methods in molecular biology (Clifton, N.J.)

    2017  Volume 1682, Page(s) 73–88

    Abstract: TEM is an important method for the characterization of size and shape of nanoparticles as it can directly visualize single particles and even their inner architecture. Imaging of metal particles in the electron microscope is quite straightforward due to ... ...

    Abstract TEM is an important method for the characterization of size and shape of nanoparticles as it can directly visualize single particles and even their inner architecture. Imaging of metal particles in the electron microscope is quite straightforward due to their high density and stable structure, but the structure of soft material nanoparticles, such as liposomes, needs to be preserved for the electron microscope. The best method to visualize liposomes close to their native structure is cryo-electron microscopy, where thin films of suspensions are plunge frozen to create vitrified ice films that can be imaged directly in the electron microscope under liquid nitrogen temperature. Although subject to artifacts, negative staining TEM can also be a useful method to image liposomes, as it is faster and simpler than cryo-EM, and requires less advanced equipment.
    MeSH term(s) Cryoelectron Microscopy/methods ; Freezing ; Liposomes/ultrastructure ; Microscopy, Electron, Transmission/methods ; Negative Staining/methods
    Chemical Substances Liposomes
    Language English
    Publishing date 2017-10-16
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ISSN 1940-6029
    ISSN (online) 1940-6029
    DOI 10.1007/978-1-4939-7352-1_8
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  2. Book ; Thesis: Lipopolysaccharid-Erkennung durch das P22-Tailspikeprotein

    Baxa, Ulrich

    biophysikalisch-chemische Analyse einer Virus-Rezeptor-Interaktion

    1998  

    Author's details vorgelegt von Ulrich Baxa
    Language German
    Size 123 S. : Ill., graph. Darst.
    Document type Book ; Thesis
    Thesis / German Habilitation thesis Regensburg, Univ., Diss., 1998
    HBZ-ID HT010627710
    Database Catalogue ZB MED Medicine, Health

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  3. Article ; Online: Self-Competitive Inhibition of the Bacteriophage P22 Tailspike Endorhamnosidase by O-Antigen Oligosaccharides.

    Baxa, Ulrich / Weintraub, Andrej / Seckler, Robert

    Biochemistry

    2020  Volume 59, Issue 51, Page(s) 4845–4855

    Abstract: The P22 tailspike endorhamnosidase confers the high specificity of bacteriophage P22 for some serogroups ... ...

    Abstract The P22 tailspike endorhamnosidase confers the high specificity of bacteriophage P22 for some serogroups of
    MeSH term(s) Bacteriophage P22/enzymology ; Catalytic Domain ; Fluorescent Dyes/chemistry ; Glycoside Hydrolases/antagonists & inhibitors ; Glycoside Hydrolases/chemistry ; Glycoside Hydrolases/metabolism ; Hydrolysis ; O Antigens/chemistry ; O Antigens/metabolism ; Oligosaccharides/chemistry ; Oligosaccharides/metabolism ; Protein Binding ; Salmonella enterica/chemistry ; Viral Tail Proteins/antagonists & inhibitors ; Viral Tail Proteins/chemistry ; Viral Tail Proteins/metabolism
    Chemical Substances Fluorescent Dyes ; O Antigens ; Oligosaccharides ; Viral Tail Proteins ; Glycoside Hydrolases (EC 3.2.1.-) ; endorhamnosidase (EC 3.2.1.-) ; tailspike protein, bacteriophage (EC 3.2.1.-)
    Language English
    Publishing date 2020-12-16
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1108-3
    ISSN 1520-4995 ; 0006-2960
    ISSN (online) 1520-4995
    ISSN 0006-2960
    DOI 10.1021/acs.biochem.0c00872
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  4. Article: Self-Competitive Inhibition of the Bacteriophage P22 Tailspike Endorhamnosidase by O-Antigen Oligosaccharides

    Baxa, Ulrich / Weintraub, Andrej / Seckler, Robert

    Biochemistry. 2020 Dec. 16, v. 59, no. 51

    2020  

    Abstract: The P22 tailspike endorhamnosidase confers the high specificity of bacteriophage P22 for some serogroups of Salmonella differing only slightly in their O-antigen polysaccharide. We used several biophysical methods to study the binding and hydrolysis of O- ...

    Abstract The P22 tailspike endorhamnosidase confers the high specificity of bacteriophage P22 for some serogroups of Salmonella differing only slightly in their O-antigen polysaccharide. We used several biophysical methods to study the binding and hydrolysis of O-antigen fragments of different lengths by P22 tailspike protein. O-Antigen saccharides of defined length labeled with fluorophors could be purified with higher resolution than previously possible. Small amounts of naturally occurring variations of O-antigen fragments missing the nonreducing terminal galactose could be used to determine the contribution of this part to the free energy of binding to be ∼7 kJ/mol. We were able to show via several independent lines of evidence that an unproductive binding mode is highly favored in binding over all other possible binding modes leading to hydrolysis. This is true even under circumstances under which the O-antigen fragment is long enough to be cleaved efficiently by the enzyme. The high-affinity unproductive binding mode results in a strong self-competitive inhibition in addition to product inhibition observed for this system. Self-competitive inhibition is observed for all substrates that have a free reducing end rhamnose. Naturally occurring O-antigen, while still attached to the bacterial outer membrane, does not have a free reducing end and therefore does not perform self-competitive inhibition.
    Keywords Gibbs free energy ; O-antigens ; Salmonella ; bacterial outer membranes ; bacteriophages ; enzymes ; galactose ; hydrolysis ; length ; oligosaccharides ; rhamnose ; serotypes
    Language English
    Dates of publication 2020-1216
    Size p. 4845-4855.
    Publishing place American Chemical Society
    Document type Article
    Note NAL-light
    ZDB-ID 1108-3
    ISSN 1520-4995 ; 0006-2960
    ISSN (online) 1520-4995
    ISSN 0006-2960
    DOI 10.1021/acs.biochem.0c00872
    Database NAL-Catalogue (AGRICOLA)

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  5. Article: Structural basis of infectious and non-infectious amyloids.

    Baxa, Ulrich

    Current Alzheimer research

    2008  Volume 5, Issue 3, Page(s) 308–318

    Abstract: Amyloid fibrils are elongated protein aggregates well known for their association with many human diseases. However, similar structures have also been found in other organisms and amyloid fibrils can also be formed in vitro by other proteins usually ... ...

    Abstract Amyloid fibrils are elongated protein aggregates well known for their association with many human diseases. However, similar structures have also been found in other organisms and amyloid fibrils can also be formed in vitro by other proteins usually under non-physiological conditions. In all cases, these fibrils assemble in a nucleated polymerization reaction with a pronounced lag phase that can be eliminated by supplying pre-formed fibrils as seeds. Once formed, the fibrils are usually very stable, except for their tendency to break into smaller pieces forming more growing ends in the process. These properties give amyloid fibers a self-replicating character dependent only on a source of soluble protein. For some systems and under certain circumstances this can lead to infectious protein structures, so-called prions, that can be passed from one organism to another as in the transmissible spongiform encephalopathies and in fungal prion systems. Structural details about these processes have emerged only recently, mostly on account of the inability of traditional high-resolution methods to deal with insoluble, filamentous specimens. In consequence, current models for amyloid fibrils are based on fewer constraints than common atomic-resolution structures. This review gives an overview of the constraints used for the development of amyloid models and the methods used to derive them. The principally possible structures will be introduced by discussing current models of amyloid fibrils from Alzheimer's beta-peptide, amylin and several fungal systems. The infectivity of some amyloids under specific conditions might not be due to a principal structural difference between infectious and non-infectious amyloids, but could result from an interplay of the rates for filament nucleation, growth, fragmentation, and clearance.
    MeSH term(s) Amyloid/chemistry ; Animals ; Humans ; Models, Molecular ; Prions/chemistry ; Protein Conformation ; Protein Folding
    Chemical Substances Amyloid ; Prions
    Language English
    Publishing date 2008-06-07
    Publishing country United Arab Emirates
    Document type Journal Article ; Research Support, N.I.H., Intramural ; Review
    ZDB-ID 2205170-3
    ISSN 1567-2050
    ISSN 1567-2050
    DOI 10.2174/156720508784533367
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  6. Article ; Online: Design of a Multicompartment Hydrogel that Facilitates Time-Resolved Delivery of Combination Therapy and Synergized Killing of Glioblastoma.

    Majumder, Poulami / Baxa, Ulrich / Walsh, Scott T R / Schneider, Joel P

    Angewandte Chemie (International ed. in English)

    2018  Volume 57, Issue 46, Page(s) 15040–15044

    Abstract: There is significant current interest in identifying new combination therapies that synergize to treat disease, and it is becoming increasingly clear that the temporal resolution of their administration greatly impacts efficacy. To facilitate effective ... ...

    Abstract There is significant current interest in identifying new combination therapies that synergize to treat disease, and it is becoming increasingly clear that the temporal resolution of their administration greatly impacts efficacy. To facilitate effective delivery, a multicompartment hydrogel material was developed that is composed of spherical vesicles interlaced within a self-assembled peptide-based network of physically crosslinked fibrils that allows time-resolved independent co-delivery of small molecules. This material architecture effectively delivers the EGFR kinase inhibitor Erlotinib (ERL) and Doxorubicin (DOX, DNA intercalator) in an ERL→DOX sequential manner to synergistically kill glioblastoma, the most aggressive form of brain cancer.
    MeSH term(s) Antineoplastic Agents/administration & dosage ; Antineoplastic Agents/pharmacokinetics ; Antineoplastic Agents/pharmacology ; Apoptosis/drug effects ; Brain Neoplasms/drug therapy ; Brain Neoplasms/pathology ; Cell Line, Tumor ; Doxorubicin/administration & dosage ; Doxorubicin/pharmacokinetics ; Doxorubicin/pharmacology ; Drug Carriers/chemistry ; Drug Delivery Systems ; Drug Synergism ; Erlotinib Hydrochloride/administration & dosage ; Erlotinib Hydrochloride/pharmacokinetics ; Erlotinib Hydrochloride/pharmacology ; Glioblastoma/drug therapy ; Glioblastoma/pathology ; Humans ; Hydrogels/chemistry ; Peptides/chemistry ; Protein Kinase Inhibitors/administration & dosage ; Protein Kinase Inhibitors/pharmacokinetics ; Protein Kinase Inhibitors/pharmacology
    Chemical Substances Antineoplastic Agents ; Drug Carriers ; Hydrogels ; Peptides ; Protein Kinase Inhibitors ; Doxorubicin (80168379AG) ; Erlotinib Hydrochloride (DA87705X9K)
    Language English
    Publishing date 2018-10-18
    Publishing country Germany
    Document type Journal Article ; Research Support, N.I.H., Intramural
    ZDB-ID 2011836-3
    ISSN 1521-3773 ; 1433-7851
    ISSN (online) 1521-3773
    ISSN 1433-7851
    DOI 10.1002/anie.201806483
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  7. Article ; Online: Immunoelectron Microscopy for Visualization of Nanoparticles.

    Anderson, Sarah R / Parmiter, David / Baxa, Ulrich / Nagashima, Kunio

    Methods in molecular biology (Clifton, N.J.)

    2017  Volume 1682, Page(s) 65–71

    Abstract: Immunoelectron microscopy (IEM) on a solid phase such as a carbon film is a fast and powerful way to detect and visualize surface antigens on nanoparticles by using a transmission electron microscope (TEM). Nanoparticles, in particular ones for medical ... ...

    Abstract Immunoelectron microscopy (IEM) on a solid phase such as a carbon film is a fast and powerful way to detect and visualize surface antigens on nanoparticles by using a transmission electron microscope (TEM). Nanoparticles, in particular ones for medical applications, are often modified on the surface with soft materials to make them more soluble, less toxic, or targetable to cancerous tumors. Imaging the soft material on the surface of solid nanoparticles by electron microscopy is often a challenge. IEM can overcome this issue in cases where antibodies to any of the surface material are available, which is often the case for proteins, but also for commonly used materials such as polyethylene glycol (PEG). This effective procedure has been used traditionally for viruses and macromolecules, but it can be directly applied to nanoparticles.
    MeSH term(s) Immunohistochemistry/methods ; Microscopy, Immunoelectron/methods ; Nanoparticles/ultrastructure ; Nanotechnology/methods ; Negative Staining/methods
    Language English
    Publishing date 2017-10-16
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural
    ISSN 1940-6029
    ISSN (online) 1940-6029
    DOI 10.1007/978-1-4939-7352-1_7
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  8. Article: The National Cryo-EM Facility at Frederick National Laboratory: Operational Procedures, Methods and Outputs.

    Baxa, Ulrich / Edwards, Thomas J / Hutchison, Matt / Wier, Adam D / Finney, Joseph / Wang, Helen / Subramaniam, Sriram

    Microscopy today

    2020  Volume 28, Issue 3, Page(s) 12–17

    Abstract: The National Cryo-Electron Microscopy Facility (NCEF) at the National Cancer Institute was launched in May of 2017 to provide free and rapid access to high resolution cryo-EM data collection to United States researchers working on problems of broad ... ...

    Abstract The National Cryo-Electron Microscopy Facility (NCEF) at the National Cancer Institute was launched in May of 2017 to provide free and rapid access to high resolution cryo-EM data collection to United States researchers working on problems of broad general relevance to cancer biology. The decision about suitability of projects for data collection is made on a first-come, first-served basis by NCEF staff, and is based solely on the quality of the screening images provided without need for a scientific proposal. Here, we provide an overview of the operation of the facility, typical data collection procedures and some insights that have emerged from the structures reported from data collected at the facility.
    Language English
    Publishing date 2020-05-18
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2139756-9
    ISSN 2150-3583 ; 1551-9295
    ISSN (online) 2150-3583
    ISSN 1551-9295
    DOI 10.1017/s1551929520000851
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  9. Article ; Online: Autophosphorylation-induced self-assembly and STIL-dependent reinforcement underlie Plk4's ring-to-dot localization conversion around a human centriole.

    Park, Jung-Eun / Meng, Lingjun / Ryu, Eun Kyoung / Nagashima, Kunio / Baxa, Ulrich / Bang, Jeong Kyu / Lee, Kyung S

    Cell cycle (Georgetown, Tex.)

    2020  Volume 19, Issue 24, Page(s) 3419–3436

    Abstract: Polo-like kinase 4 (Plk4) is a key regulator of centriole biogenesis. Studies have shown that Plk4 undergoes dynamic relocalization from a ring-like pattern around a centriole to a dot-like morphology at the procentriole assembly site and this event is ... ...

    Abstract Polo-like kinase 4 (Plk4) is a key regulator of centriole biogenesis. Studies have shown that Plk4 undergoes dynamic relocalization from a ring-like pattern around a centriole to a dot-like morphology at the procentriole assembly site and this event is central for inducing centriole biogenesis. However, the detailed mechanisms underlying Plk4's capacity to drive its symmetry-breaking ring-to-dot relocalization remain largely unknown. Here, we showed that Plk4 self-initiates this process in an autophosphorylation-dependent manner and that STIL, its downstream target, is not required for this event. Time-dependent analyses with mEOS-fused photoconvertible Plk4 revealed that a portion of ring-state Plk4 acquires a capacity, presumably through autophosphorylation, to linger around a centriole, ultimately generating a dot-state morphology. Interestingly, Plk4 WT, but not its catalytically inactive mutant, showed the ability to form a nanoscale spherical assembly in the cytosol of human cells or heterologous
    MeSH term(s) Biocatalysis ; Cell Cycle/genetics ; Cell Line, Tumor ; Centrioles/metabolism ; Cytosol/metabolism ; Escherichia coli/metabolism ; Escherichia coli Proteins/metabolism ; HEK293 Cells ; Humans ; Intracellular Signaling Peptides and Proteins/chemistry ; Intracellular Signaling Peptides and Proteins/genetics ; Intracellular Signaling Peptides and Proteins/metabolism ; Osteosarcoma/pathology ; Phosphorylation ; Proteasome Endopeptidase Complex/metabolism ; Protein Binding ; Protein Domains ; Protein Serine-Threonine Kinases/genetics ; Protein Serine-Threonine Kinases/metabolism ; Proteolysis ; RNA Interference ; Signal Transduction/genetics ; Transfection
    Chemical Substances Escherichia coli Proteins ; Intracellular Signaling Peptides and Proteins ; STIL protein, human ; PLK4 protein, human (EC 2.7.1.-) ; Protein Serine-Threonine Kinases (EC 2.7.11.1) ; Proteasome Endopeptidase Complex (EC 3.4.25.1)
    Language English
    Publishing date 2020-12-15
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2146183-1
    ISSN 1551-4005 ; 1538-4101 ; 1554-8627
    ISSN (online) 1551-4005
    ISSN 1538-4101 ; 1554-8627
    DOI 10.1080/15384101.2020.1843772
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    Zs.A 5881: Show issues Location:
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  10. Article ; Online: The crystal structure of human GlnRS provides basis for the development of neurological disorders.

    Ognjenović, Jana / Wu, Jiang / Matthies, Doreen / Baxa, Ulrich / Subramaniam, Sriram / Ling, Jiqiang / Simonović, Miljan

    Nucleic acids research

    2016  Volume 44, Issue 7, Page(s) 3420–3431

    Abstract: Cytosolic glutaminyl-tRNA synthetase (GlnRS) is the singular enzyme responsible for translation of glutamine codons. Compound heterozygous mutations in GlnRS cause severe brain disorders by a poorly understood mechanism. Herein, we present crystal ... ...

    Abstract Cytosolic glutaminyl-tRNA synthetase (GlnRS) is the singular enzyme responsible for translation of glutamine codons. Compound heterozygous mutations in GlnRS cause severe brain disorders by a poorly understood mechanism. Herein, we present crystal structures of the wild type and two pathological mutants of human GlnRS, which reveal, for the first time, the domain organization of the intact enzyme and the structure of the functionally important N-terminal domain (NTD). Pathological mutations mapping in the NTD alter the domain structure, and decrease catalytic activity and stability of GlnRS, whereas missense mutations in the catalytic domain induce misfolding of the enzyme. Our results suggest that the reduced catalytic efficiency and a propensity of GlnRS mutants to misfold trigger the disease development. This report broadens the spectrum of brain pathologies elicited by protein misfolding and provides a paradigm for understanding the role of mutations in aminoacyl-tRNA synthetases in neurological diseases.
    MeSH term(s) Amino Acyl-tRNA Synthetases/chemistry ; Amino Acyl-tRNA Synthetases/genetics ; Amino Acyl-tRNA Synthetases/ultrastructure ; Crystallography, X-Ray ; Humans ; Models, Molecular ; Mutation ; Nervous System Diseases/genetics ; Protein Folding ; Protein Structure, Tertiary
    Chemical Substances Amino Acyl-tRNA Synthetases (EC 6.1.1.-) ; glutaminyl-tRNA synthetase (EC 6.1.1.18)
    Language English
    Publishing date 2016-04-20
    Publishing country England
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 186809-3
    ISSN 1362-4962 ; 1362-4954 ; 0301-5610 ; 0305-1048
    ISSN (online) 1362-4962 ; 1362-4954
    ISSN 0301-5610 ; 0305-1048
    DOI 10.1093/nar/gkw082
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