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1. Modeling protein–nucleic acid complexes with extremely large conformational changes using Flex‐LZerD

   https://doi.org/10.1002/pmic.202200322  

   Christoffer, Charles; Kihara, Daisuke (December 2022, PROTEOMICS)

   Abstract Proteins and nucleic acids are key components in many processes in living cells, and interactions between proteins and nucleic acids are often crucial pathway components. In many cases, large flexibility of proteins as they interact with nucleic acids is key to their function. To understand the mechanisms of these processes, it is necessary to consider the 3D atomic structures of such protein–nucleic acid complexes. When such structures are not yet experimentally determined, protein docking can be used to computationally generate useful structure models. However, such docking has long had the limitation that the consideration of flexibility is usually limited to small movements or to small structures. We previously developed a method of flexible protein docking which could model ordered proteins which undergo large‐scale conformational changes, which we also showed was compatible with nucleic acids. Here, we elaborate on the ability of that pipeline, Flex‐LZerD, to model specifically interactions between proteins and nucleic acids, and demonstrate that Flex‐LZerD can model more interactions and types of conformational change than previously shown. 

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2. Abiotic stressors impact outer membrane vesicle composition in a beneficial rhizobacterium: Raman spectroscopy characterization

   https://doi.org/10.1038/s41598-020-78357-4  

   Potter, Matthew; Hanson, Cynthia; Anderson, Anne J.; Vargis, Elizabeth; Britt, David W. (December 2020, Scientific Reports)

   Abstract Outer membrane vesicles (OMVs) produced by Gram-negative bacteria have roles in cell-to-cell signaling, biofilm formation, and stress responses. Here, the effects of abiotic stressors on OMV contents and composition from biofilm cells of the plant health-promoting bacteriumPseudomonas chlororaphisO6 (PcO6) are examined. Two stressors relevant to this root-colonizing bacterium were examined: CuO nanoparticles (NPs)-a potential fertilizer and fungicide- and H₂O₂-released from roots during plant stress responses. Atomic force microscopy revealed 40–300 nm diameter OMVs from control and stressed biofilm cells. Raman spectroscopy with linear discriminant analysis (LDA) was used to identify changes in chemical profiles ofPcO6 cells and resultant OMVs according to the cellular stressor with 84.7% and 83.3% accuracies, respectively. All OMVs had higher relative concentrations of proteins, lipids, and nucleic acids thanPcO6 cells. The nucleic acid concentration in OMVs exhibited a cellular stressor-dependent increase: CuO NP-induced OMVs > H₂O₂-induced OMVs > control OMVs. Biochemical assays confirmed the presence of lipopolysaccharides, nucleic acids, and protein in OMVs; however, these assays did not discriminate OMV composition according to the cellular stressor. These results demonstrate the sensitivity of Raman spectroscopy using LDA to characterize and distinguish cellular stress effects on OMVs composition and contents. 

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3. Proximal Molecular Probe Transfer (PROMPT), a new approach for identifying sites of protein/nucleic acid interaction in cells by correlated light and electron microscopy

   https://doi.org/10.1038/s41598-023-45413-8  

   Castillon, Guillaume A; Phan, Sebastien; Hu, Junru; Boassa, Daniela; Adams, Stephen R; Ellisman, Mark H (December 2023, Scientific Reports)

   Abstract The binding and interaction of proteins with nucleic acids such as DNA and RNA constitutes a fundamental biochemical and biophysical process in all living organisms. Identifying and visualizing such temporal interactions in cells is key to understanding their function. To image sites of these events in cells across scales, we developed a method, named PROMPT for PROximal Molecular Probe Transfer, which is applicable to both light and correlative electron microscopy. This method relies on the transfer of a bound photosensitizer from a protein known to associate with specific nucleic acid sequence, allowing the marking of the binding site on DNA or RNA in fixed cells. The method produces a fluorescent mark at the site of their interaction, that can be made electron dense and reimaged at high resolution in the electron microscope. As proof of principle, we labeled in situ the interaction sites between the histone H2B and nuclear DNA. As an example of application for specific RNA localizations we labeled different nuclear and nucleolar fractions of the protein Fibrillarin to mark and locate where it associates with RNAs, also using electron tomography. While the current PROMPT method is designed for microscopy, with minimal variations, it can be potentially expanded to analytical techniques. 

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4. Lipofection mediated transfection fails for sea urchin coelomocytes

   https://doi.org/10.1371/journal.pone.0267911  

   Barela Hudgell, Megan A.; Smith, L. Courtney (May 2022, PLOS ONE)

   Escriva, Hector (Ed.)

   Molecular cloning, gene manipulation, gene expression, protein function, and gene regulation all depend on the introduction of nucleic acids into target cells. Multiple methods have been developed to facilitate such delivery including instrument based microinjection and electroporation, biological methods such as transduction, and chemical methods such as calcium phosphate precipitation, cationic polymers, and lipid based transfection, also known as lipofection. Here we report attempts to lipofect sea urchin coelomocytes using DOTAP lipofection reagent packaged with a range of molecules including fluorochromes, in addition to expression constructs, amplicons, and RNA encoding GFP. DOTAP has low cytotoxicity for coelomocytes, however, lipofection of a variety of molecules fails to produce any signature of success based on results from fluorescence microscopy and flow cytometry. While these results are negative, it is important to report failed attempts so that others conducting similar research do not repeat these approaches. Failure may be the outcome of elevated ionic strength of the coelomocyte culture medium, uptake and degradation of lipoplexes in the endosomal-lysosomal system, failure of the nucleic acids to escape the endosomal vesicles and enter the cytoplasm, and difficulties in lipofecting primary cultures of phagocytic cells. We encourage others to build on this report by using our information to optimize lipofection with a range of other approaches to work towards establishing a successful method of transfecting adult cells from marine invertebrates. 

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5. Biolistic approach for transient gene expression studies in plants

   Lacroix, Benoit; Citovsky, Vitaly (April 2020, Methods in molecular biology)

   Since its inception in the late 1980s, the delivery of exogenous nucleic acids into living cells via high-velocity microprojectiles (biolistic, or microparticle bombardment) has been an invaluable tool for both agricultural and fundamental plant research. Here, we review the technical aspects and the major applications of the biolistic method for studies involving transient gene expression in plant cells. These studies cover multiple areas of plant research, including gene expression, protein subcellular localization and cell-to-cell movement, plant virology, silencing, and the more recently developed targeted genome editing via transient expression of customized endonucleases. 

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