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Modeling sugars with Coot and Phenix
by Emilia C. Arturo (Emily) 07 Jan '21

07 Jan '21

Hello All, I have several questions regarding sugar modeling. These are questions for both Coot (0.9.4-pre/CCPEM) and Phenix (1.18.2-3874) usage (on a Mac) for modeling as correctly as possible several N-linked glycosylation (i.e. not ligand) sugars within a protein, and about the approach as it pertains to higher resolution X-ray maps (better than 2A) or to lower resolution EM maps (~3-4A). I am new to the world of glycoproteins and cryoEM, not new to model building or X-ray crystallography, and would welcome any advice or insight. For relatively low resolution maps, where sugar moieties cannot be placed unambiguously, in theory (say Agirre (2017) and Emsley and Crispin (2018)) pyranose placement within the map should be quite highly restrained by ideal geometry for the specific sugar expected from prior knowledge. In practice, however, it’s not entirely clear how to maintain these restraints on pyranose geometry and conformation during manual building in Coot, or how to apply any special restraints in Phenix. The Glyco module of Coot does indeed place fine looking Asn-NAGs after a few iterations of manual placing and refining to account for the poor resolution of the acetyl group, just as discussed by Emsley and Crispin (2018). However, the validation report that is obtained from the OneDep system at the rcsb web server for the resulting structure shows many outliers in bonds and angles within the NAG or between the NAG and protein Asn residue. In Coot I have experimented with various restraints (in the R/RC menu), including decreasing the Refinement weight/weight matrix to zero, or some small non-zero number, thinking this places less weight on the map signal and more on the ideal values within Coot’s libraries. I have tried a variety of refinement restraint combinations in Coot to address individual bonds and angles outliers within the sugar, but the rcsb validation report still finds departures from ideal geometry. Meanwhile, in Phenix I don’t do anything specific for the refinement of glycosylation sugars (should I?) other than apply the appropriate restraints for any low resolution EM map; are there specific restraints files I ought to be using within Phenix real space refine jobs for N-linked sugars? Then I noticed that loads of existing PDB entries containing N-linked glycans contain similar outliers in pyranose geometry. So this prompted me to wonder whether we’re not doing things right, that in practice we’re not correctly following what’s advised in theory, or whether this is just the state of model building currently. Could someone more experienced than am I on sugar building please comment here on how exactly to get the sugars better built? e.g. what buttons to press and why, in Phenix and/or in Coot. Or is this a tolerable situation where sugar geometries differ from ideal even at low resolution? Is it perhaps a matter of different targets being used for PDB validation by the rcsb versus by Coot? It turns out that regarding higher resolution maps I am also unsure of exactly how to apply restraints within Coot. For example, using PDB ID 5VAA and its map with a reported resolution of 1.55A, I centered on Asn297 and its associated glycosylation sugars. I experimented with refinement strategies (i.e. the settings of R/RC), thinking that the best approach would be little restraint on ideal geometry and higher weight on the map signal. But no matter what combination of restraints I used, I was unable to keep the model locally from distorting; i.e. the deposited model versus map looks great, but within Coot I find a hundred ways to destroy it. I must be doing something wrong. Any advice or references you’d recommend would be greatly appreciated. Thanks. -- "Study as if you were going to live forever; live as if you were going to die tomorrow." - Maria Mitchell "I'm not afraid of storms for I'm learning to sail my ship." - Louisa May Alcott

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post-doc position at KU Leuven, ligand-gated ion channels
by Chris Ulens 05 Jan '21

05 Jan '21

A post-doctoral position is available at the Laboratory of Prof. Chris Ulens, KU Leuven, Belgium (http://www.xtal.be <http://www.xtal.be/>). The research in the Laboratory of Structural Neurobiology is aimed at understanding the molecular mechanism of ligand-gated ion channels. Our methods rely on X-ray crystallography and cryo-EM in combination with electrophysiological recordings and fluorescence-based techniques. Our laboratory hosts an integrated macromolecular crystallization facility with a Mosquito crystallization robot and two RockImagers. We have access to a 200 kV Glacios microscope on campus as well as 300 kV JEOL CryoARM300 at the nearby EM facility in Brussels. Current projects are situated at the crossroads of structural elucidation and drug discovery of different pentameric ligand-gated ion channels. We would like to recruit a post-doc with prior experience in cryo-EM or X-ray crystallography of membrane proteins. The successful candidate: - easily communicates in an open verbal manner and has a team player spirit - has an ambitious work ethic - critically contributes to writing of manuscripts and grant proposals - makes efforts to obtain independent funding - meets intermediate deadlines and brings projects to a successful end - fuels internal discussions of recent publications in the field - sets an example to younger PhD students in the lab - identifies directions for future scientific research The position is open immediately and applications will be accepted until the position is filled. Applicants are requested to submit a CV with publication list and two references. E-mail to chris.ulens(a)kuleuven.be <mailto:[email protected]> Selection of recent publications: A lipid site shapes the agonist response of a pentameric ligand-gated ion channel. Hénault CM, Govaerts C, Spurny R, Brams M, Estrada-Mondragon A, Lynch J, Bertrand D, Pardon E, Evans GL, Woods K, Elberson BW, Cuello LG, Brannigan G, Nury H, Steyaert J, Baenziger JE, Ulens C. Nat Chem Biol. 2019;15(12):1156-1164. doi: 10.1038/s41589-019-0369-4. Modulation of the Erwinia ligand-gated ion channel (ELIC) and the 5-HT3 receptor via a common vestibule site. Brams M, Govaerts C, Kambara K, Price KL, Spurny R, Gharpure A, Pardon E, Evans GL, Bertrand D, Lummis SC, Hibbs RE, Steyaert J, Ulens C. Elife. 2020;9:e51511. doi: 10.7554/eLife.51511. The structural basis for an on-off switch controlling Gβγ-mediated inhibition of TRPM3 channels. Behrendt M, Gruss F, Enzeroth R, Dembla S, Zhao S, Crassous PA, Mohr F, Nys M, Louros N, Gallardo R, Zorzini V, Wagner D, Economou A, Rousseau F, Schymkowitz J, Philipp SE, Rohacs T, Ulens C, Oberwinkler J. Proc Natl Acad Sci U S A. 2020;117(46):29090-29100. doi: 10.1073/pnas.2001177117.

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Bad geometry for DNA after Real-Space-Refine
by Jobichen Chacko 05 Jan '21

05 Jan '21

Dear BB, I am using phenix real space refinement for refining a cryo-EM model of protein-DNA complex. However after refinement the structure of the dna strands are twisted in a very bad geometry compared to the initial input model. I am using version 1.8 for this project, also tried couple of other versions as well, but the same problem happened. How to rectify this issue? Thank you. Jobi

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Variation in bonds after loading restraints
by Vatsal Purohit 02 Jan '21

02 Jan '21

Hello, I’ve been having issues with obtaining consistent number of bonds after generating .cif files using eLBOW. To generate the .cif file for an NADH molecule on eLBOW, I’ve been using a SMILE string generated using Chemdraw and a template .pdb file that was generated after using LigFit with a ligand .pdb model (also initially generated using a SMILE string). However, I find that when I load the restraints the bonds in the molecule only show correctly on the older version of coot (0.8.9.2). The double bonds on the adenine ring don’t appear in the latest version of coot (0.9.3) and the double bonds on the molecule don’t show up at all when I load the .cif file on REEL. Is there a reason why they could be inconsistent? Could I be viewing them incorrectly on REEL? Any thoughts on this would be appreciated! I’ve attached the SMILE string, template .pdb file and final .cif file in this email for your reference. Regards, Vatsal PhD Candidate, Stauffacher Lab, Dept. of Biology, Purdue University PULSe-Biophysics and Structural Biology training group vpurohi(a)purdue.edu<mailto:[email protected]> | 346-719-9409

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Calculating the transformation matrix of density map alignment
by Ahmad Khalifa 23 Dec '20

23 Dec '20

I have two density maps that I'm trying to align, or more precisely, calculate the transformation matrix (rotation and translation) of their alignment (moving one map and aligning it with the other map). Is there a way to accomplish that using phenix or any other tool? Thanks a lot and happy holidays.

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Post-doctoral vacancy in cryoEM of viruses
by Hasan, Syed Saif 22 Dec '20

22 Dec '20

Dear Colleagues, A vacancy for a post-doctoral researcher is available immediately in my lab in the University of Maryland Center for Biomolecular Therapeutics located on the campus of Institute for Bioscience and Biotechnology Research (IBBR; https://www.ibbr.umd.edu/profiles/s-saif-hasan) in Rockville MD. We use high-resolution single particle cryoEM and X-ray crystallography to investigate how viruses utilize structural similarities with host proteins to hijack inter-organelle communication. Prior experience in insect cell culture for recombinant protein production is desirable. Expertise in cryoEM or X-ray crystallography will be advantageous. Candidates who have recently completed their PhD are encouraged to apply. IBBR is located 20 miles north-west of Washington DC. In IBBR, you will have in-house access to a 200 kV Talos Arctica with a Falcon 3EC DED and a 200 kV Glacios with a K3 DED and a Volta Phase Plate (VPP). We have a Vitrobot Mark IV and a Cp3 cryo-plunger for sample preparation. We have off-site access to a Titan Krios microscope equipped with DED and VPP. For X-ray crystallography, we have access to a Mosquito crystallization robot. Data collection is usually performed at synchrotrons. Our research is highly collaborative and is supported by wonderful colleagues who help us out with their expertise in NMR spectroscopy, lipidomics, HDX-MS, MD simulations, computer assisted drug design, and cellular imaging. Interested candidates should send their CV and a cover letter to me at sshasan(a)som.umaryland.edu ************************************************************************************************ The University of Maryland, Baltimore is an Equal Opportunity, Affirmative Action employer. Minorities, women, individuals with disabilities and protected veterans are encouraged to apply. ************************************************************************************************ Saif S. Saif Hasan, PhD Assistant Professor Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine 108 N. Greene Street, Baltimore MD 21201 https://www.medschool.umaryland.edu/profiles/Hasan-S-Saif-Hasan-Syed-Saif/ Associate Member Program in Oncology, University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center (UMGCCC) 22 S. Greene Street, Baltimore MD 21201 Office and Laboratory Address: Center for Biomolecular Therapeutics, Institute for Bioscience and Biotechnology Research (IBBR) 9600 Gudelsky Drive, Rockville MD 20850 https://www.ibbr.umd.edu/profiles/s-saif-hasan Phone: 240-314-6396 Fax: 240-314-6225

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Coot+Phenix issue
by Ashima Chopra 21 Dec '20

21 Dec '20

Hi all, I am running a refinement on Phenix for one structure, as I work on the Molprobity corrections from another refined structure in Coot. My Coot connects to Phenix so I can navigate through the Molprobity list easily, however the tmp.refine files from the first refinement keep popping up and replacing the current maps I have open. Is it possible to be connected to Phenix and define which project to display the maps/models from? Thanks, Ashima Ashima Chopra Graduate Assistant Eddy Arnold Laboratory Department of Chemistry and Chemical Biology/ Center for Advanced Biotechnology and Medicine Rutgers University, New Brunswick

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ASAPpdb - pledge to release data with preprints
by James Fraser 16 Dec '20

16 Dec '20

Fellow structural biologists - The revolution in publishing made possible by preprints calls for a re-evaluation of data disclosure practices in structural biology. While journal review processes take weeks, months, or even years, preprints allow researchers to rapidly communicate their findings to the community. However, withholding access to PDB files that accompany preprints inhibits the progress towards scientific discovery which preprints can enable. There is nothing more disappointing than reading a great preprint and not being able to open the coordinates and inspect the density! Sign the pledge to publicly release PDB files (and associated structure factor, restraint, and map files) with deposition of preprints here: https://asapbio.org/asappdb All the best, James PS> Apologies for the cross post to multiple bb's -- James Fraser - http://www.fraserlab.com - @fraser_lab jaimefraser(a)gmail.com // jfraser(a)fraserlab.com he/his/him (please do NOT use james.fraser(a)ucsf.edu)

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MicroED workshop 2020
by Johan Hattne 13 Dec '20

13 Dec '20

Dear all; We are pleased to announce the 6th MicroED workshop to be held on December 21, 2020. This will be a free virtual event. Please register at the following website to receive your link https://cryoem.ucla.edu/course Topics covered will include all aspects of microcrystal electron diffraction (MicroED) of diverse samples such as soluble proteins, membrane proteins, small molecules, natural products, and other materials. We will cover 1. Sample preparation methodologies 2. EPU-D for data collection 3. Camera systems and performance 4. FIB-milling procedures for soluble and membrane protein samples 5. Data analysis software, refinement, and structure solution The schedule is available on the registration page. // Sincerely; The organizing committee (Tamir Gonen, Brandon Mercado, Brent Nannenga)

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Submission Deadline on December 14th
by Tessa Van Grack 07 Dec '20

07 Dec '20

Hi PHENIX community, The AIMS Awards Fall 2020 application deadline is just one week away! For anyone with a protein target of interest, the AIMS Award program can help you discover new molecular tools, start new drug development programs, and get published. We encourage investigators, postdocs, and graduate students worldwide to apply. The AIMS Awards program provides non-profit researchers with virtual screening and compounds for physical testing at no cost. Collaborate with us to find novel active compounds for your protein target of interest. You can fill out the short application form directly on the website: atomwise.com/aims <https://hubs.la/H0z3sT80>. Please don't hesitate to reach out to me if you have any questions! Kind regards, Tessa *Tessa Van Grack, M.S.* Partnering Associate Atomwise <https://www.atomwise.com/> | Better Medicines Faster ᐧ -- Confidentiality Notice: The information contained herein is for informational purposes only. This message is private and the information contained in this message, including any attachments, contains information that may be confidential, privileged and/or proprietary. It is intended to be read only by the individual or entity to whom it is addressed. If you are not the intended recipient, please notify the sender by replying to this message, delete the material immediately from your system and note that you must not review, disclose, copy, distribute or take any action in reliance on or in reference to this message, including any attachments. No confidentiality, privilege, or property rights are waived or lost by any errors in transmission. Any unauthorized use or disclosure of the contents of this message is not permitted and may be unlawful.

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