Hi @Nicolo-0 , No, currently, there is no option to specify that H-bonds in an H-bond group (which is part of a structural model) should be displayed between hydrogens and acceptors - they are drawn between donors and acceptors, since hydrogens might be implicit. However, we can add such an option in the next major release of SAMSON. But if you want it just for the sake of visualization, then you can try setting hydrogens as donors programatically (via Python). Note that this should be done without calling update() since this will recompute the bonds.

Dear @David-Adrian , Thank you for your feedback! We will consider this for future releases. Where would you like to install it, e.g. on another drive or a USB-stick?

Hi Luis, sorry for the delay! Could you please contact us at contact@samson-connect.net? It would be easier to chat / zoom about this so we can focus the development. Thanks! best, Stephane

Dear @DmitriyMarin Thank you for your reply! Yes, that LAMMPS wizard would be wonderful. Best regards, Patrik Molnár

Dear @sudhir , To save only the last frame in the trajectory into a PDB file, you can select a path corresponding to this trajectory and set the step to the last one in the Inspector (click Ctrl/Cmd + I to open the Inspector in SAMSON), this will update the structural model - it will correspond to the step you chose. Now you can select the structural model in the Document view and save only the selection as a PDB file, for that in the menu go to Selection > Save selection as and select the PDB format in the types of files. As for now, there is no direct way to save a .gro file from within SAMSON. The GROMACS Wizard Element saves the temporary files, including some gro files in a specific scratch folder in your user's directory, the path is different for different OS (Windows, Linux, Mac OS). You can either try looking for the Scratch/GROMACS on your system or check out the path to SAMSON's scratch folder by launching SAMSON-Core-Console executable version and checking for a line with SBGPath::getScratchPath() in the beginning of the console output. On Windows it will be something like: C:\Users\user\AppData\Local\OneAngstrom\SAMSON\DATA\0.8.3\Scratch.

Dear @sudhir , For the protein-ligand simulation, you can check out the Ligand Path Finder tutorial for Ligand Path Finder Element. You can also check out the Ligand unbinding pathway search tutorial for the free Ligand Unbinding Search Element (available only on SAMSON 0.7.0). As for saving MD trajectories, you can check out the tutorial on exporting atoms trajectories along paths which uses the Export Along Paths Element. This Element allows you to export trajectories into PDB files which you can further analyze using other software. You can also do some analysis and post-processing in SAMSON thanks to the Python Scripting Element, you can check out the Python Scripting guide for more information, for example, the Computing RMSD sample. To simulate a protein-membrane complex you can use the GROMACS Wizard Element, using this Element you can easily prepare your system for GROMACS simulation, minimize and equilibrate the structure, and simulate your system using GROMACS. See the GROMACS Wizard tutorial for more information.

Hi, Actually interactive fitting only VMD is providing and that is also very limited. VMD chops off your actual EM map according to the provided pdb model instead of fitting it into the density. So, as I want to fit multiple structures in the map, I can not do it. I was trying to fit my multi-chain PDB in the same map but it failed. Chimera do not provide interactive fitting and it fits the protein poorly in the map. Therefore, it is hard to get a proper knowledge of the conformation of any of these tools. Rest tools are more programming centric, making them hard to be used by biologists having limited programming skills like me.

Hi @Cyril, thank you very much for the idea!

Dear @Andrea , We have updated the Lennard-Jones Interaction Model SAMSON Element, now you can set the smaller epsilon parameter. The SAMSON Element should be updated automatically once you launch SAMSON with an Internet connection.

Rendering of spheres is fast, it is done on GPU, rendering of disks should not make it much faster. It is the Document view, which makes it slower for bigger systems, but it will be faster in the next SAMSON version. If you want to see the flat visualization of atoms, you can modify the rendering preferences via changing the lightning preferences in SAMSON (see User guide: Visualizing. Lightning section). Basically, in the SAMSON preferences (Ctrl/Cmd+K) go to Rendering > Lightning: set the light intensity for first and second lights to zero; set the ambient light to 1 and the Fresnel intensity to 0.

Hello @Kava ! Thank you for your interest in SAMSON. As far as we know, no one is currently working on the STL exporter. But this would be a really nice feature. For the efficiency and speed reasons, the Gaussian surface is generated on GPU. Therefore, we don't have direct access to resulting shapes and it won't be that easy to export these shapes. We will see what we can do. Another possibility is to program the Gaussian surface on CPU yourself and export the resulting shape in the STL file (see Documentation for developers).

Thank you for the suggestion, @Cyril ! Yes, for now, it is possible only with an importer for crystallographic .cif files. There is a possibility to replicate crystals thanks to the Crystal Creator App, but it does not expand them periodically with bond connections. We will see what we can do.

Thank you @Cyril for the suggestion. We will see whether to add it as a feature in the next version of SAMSON or implement it as a SAMSON Element. For now, you can use Python Scripting in SAMSON. To use the Python Scripting SAMSON Element you will need to have a specific version of Python installed. Please, check the Python Scripting installation instructions for SAMSON. You can also check the SAMSON Python Scripting tutorials and documentation. The sample script for this task can be found below. You can either copy it inside of the Python Scripting console in SAMSON, or save it as a .py file and open this file in SAMSON when you need to execute this script. ''' This example shows how to select bonds which center lies in between of two planes: z_min and z_max If you want to select bonds which center lies on a specific plane, just set z_min=z_max ''' # Get an indexer of all bonds in the active document. Here we use SAMSON Node Specification Language to get only bonds allBondsIndexer = SAMSON.getNodes('node.type bond') # two planes: 1.7A and 2.3A z_min = Quantity.angstrom(1.7) z_max = Quantity.angstrom(2.3) for bond in allBondsIndexer: # a loop over an indexer # compute the z-axis center of the bond bondCenterZ = (bond.leftAtom.getZ() + bond.rightAtom.getZ()) / 2.0 # check whether the bond lies in between of desired planes if bondCenterZ >= z_min and bondCenterZ <= z_max: # select the bond by setting the selectionFlag to True bond.selectionFlag = True allBondsIndexer.clear() # clear an indexer

There is an invert selection feature in SAMSON: right-click on the selection (either in the Document view or in the viewport), and in the context menu select Invert selection [image: 0_1549532475757_InvertSelection.png]

It works great ! Thanks a lot !