Category Archives: Hints and Tips

Words of Wisdom from final year PhD students

NB: These are entirely subjective so please ignore them all if you want.

1.     Write everything down in a searchable place 

Maybe you are gifted with a brilliant memory but, for the rest of us, write everything down (either in a notebook, or better yet, some kind of searchable typed document). This includes notes from supervisor meetings, industry meetings, clever suggestions over coffee, group meetings, etc… 

In our experience, writing things on paper is risky unless you have a decent filing system (see our desks for examples of how not to file notes). It also requires writing legibly. Typed notes are also particularly useful for saving common error messages/bug fixes/useful installation instructions/functions etc in one place so that you can easily search for them again! This can be just a word document, o rGemma showed me “Notion” which has so far been really useful (and you get to put emojis next to your notes).

This also leads to the second tip…

2.     Type up notes on papers you’ve read or use a reference manager 

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Retrieving AlphaFold models from AlphaFoldDB

There are now nearly a million AlphaFold [1] protein structure predictions openly available via AlphaFoldDB [2]. This represents a huge set of new data that can be used for the development of new methods. The options for downloading structures are either in bulk (sorted by genome), or individually from the webpage for a prediction.

If you want just a few hundred or a few thousand specific structures, across different genomes, neither of these options are particularly practical. For example, if you have several thousand experimental structures for which you have their PDB [3] code, and you want to obtain the equivalent AlphaFold predictions, there is another way!

If we take the example of the PDB’s current molecule of the month, pyruvate kinase (PDB code 4FXF), this is how you can go about downloading the equivalent AlphaFold prediction programmatically.

  1. Query UniProt [4] for the corresponding accession number – an example python script is shown below:
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Ten quick tips for proofreading your work

For my blog post, I thought I’d revisit my dark past on the other side of academic publishing when I worked as a copy editor and proofreader for two years between my undergrad and Masters. During this time, I worked primarily on review papers and news content. While I don’t claim to be a great writer or editor, I thought I’d share some easy tips to help refine your writing and make it more consistent. This is by no means an exhaustive list and probably most of them will already be familiar to you!

1. Consistency is key

I think two of the most important aspects of proofreading are ensuring consistency and using your common sense. For example, instead of agonizing over how you style a word, choose what you think is most appropriate and check that you’ve applied it consistently throughout the text. Check that style matches between the main text, headings, figure legends and footnotes. Some specific things to look for include the following:

  • Capitalization
    • If you’ve capitalized headings, has this been done throughout?
  • Italicization
    • E.g., have you italicized all your mentions of ‘in silico’? 
  • Superscript and subscript
    • E.g., is ‘half-maximal inhibitory concentration (IC50)‘ the same throughout? 
  • Numbers
    • Have you mixed up numerical and spelled-out numbers?  
    • E.g., I drank five cups of coffee and 4 cups of tea. 
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Tackling horizontal and vertical limitations

A blog post about reviewing papers and preparing papers for publication.

We start with the following premise: all papers have limitations. There is not a single paper without limitations. A method may not be generally applicable, a result may not be completely justified by the data or a theory may make restrictive assumptions. To cover all limitations would make a paper infinitely long, so we must stop somewhere.

A lot of limitations fall into the following scenario. The results or methods are presented but they could have extended them in some way. Suppose, we obtain results on a particular cell type using an immortalized cell-line. Are the results still true, if we performed the experiments on primary or patient-derived cells? If the signal from the original cells was sufficiently robust then we would hope so. However, we can not be one hundred percent sure. A similar example is a method that can be applied to a certain type of data. It may be possible to extend the method to be applied to other data types. However, this may require some new methodology. I call this flavor of limitations vertical limitations. They are vertical in the sense that they build upon an already developed result in the manuscript. For certain journals, they will require that you tackle vertical limitations by adapting the original idea or method to demonstrate broad appeal or that idea could permeate multiple fields. Most of the time, however, the premise of an approach is not to keep extending it. It works. Leave it alone. Do not ask for more. An idea done well does not need more.

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Visualise with Weight and Biases

Understanding what’s going on when you’ve started training your shiny new ML model is hard enough. Will it work? Have I got the right parameters? Is it the data? Probably.  Any tool that can help with that process is a Godsend. Weights and biases is a great tool to help you visualise and track your model throughout your production cycle. In this blog post, I’m going to detail some basics on how you can initialise and use it to visualise your next project.

Installation

To use weights and biases (wandb), you need to make an account. For individuals it is free, however, for team-oriented features, you will have to pay. Wandb can then be installed using pip or conda.

$ 	conda install -c conda-forge wandb

or 

$   pip install wandb

To initialise your project, import the package, sign in, and then use the following command using your chosen project name and username (if you want):

import wandb

wandb.login()

wandb.init(project='project1')

In addition to your project, you can also initialise a config dictionary with starting parameter values:

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Sharing Data Responsibly: The FAIR Principles

So you’ve submitted your paper, made your code publicly available, and maybe even provided documentation to ensure somebody can reproduce your work. But what about the data your work is based on? Is that readily available to your readers, too?

Maybe it’s too large to put on GitHub alongside your code. Maybe it’s sensitive, or subject to GDPR restrictions, so you can’t just stick a download link on your website. Maybe it’s in a proprietary format that needs non-open software to read. There are many reasons sharing data can be less straightforward than sharing code, and often it’s not entirely clear what ‘best practices’ are for a given situation. Data management is a complicated topic, and to do it justice would require far more than a quick blog post. Instead, I’d like to focus on a single source of guidance that serves as a useful starting point for thinking about responsible data management: the FAIR principles.

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How to prepare a molecule for RDKit

RDKit is very fussy when it comes to inputs in SDF format. Using the SDMolSupplier, we get a significant rate of failure even on curated datasets such as the PDBBind refined set. Pymol has no such scruples, and with that, I present a function which has proved invaluable to me over the course of my DPhil. For reasons I have never bothered to explore, using pymol to convert from sdf, into mol2 and back to sdf format again (adding in missing hydrogens along the way) will almost always make a molecule safe to import using RDKit:

from pathlib import Path
from pymol import cmd

def py_mollify(sdf, overwrite=False):
    """Use pymol to sanitise an SDF file for use in RDKit.

    Arguments:
        sdf: location of faulty sdf file
        overwrite: whether or not to overwrite the original sdf. If False,
            a new file will be written in the form <sdf_fname>_pymol.sdf
            
    Returns:
        Original sdf filename if overwrite == False, else the filename of the
        sanitised output.
    """
    sdf = Path(sdf).expanduser().resolve()
    mol2_fname = str(sdf).replace('.sdf', '_pymol.mol2')
    new_sdf_fname = sdf if overwrite else str(sdf).replace('.sdf', '_pymol.sdf')
    cmd.load(str(sdf))
    cmd.h_add('all')
    cmd.save(mol2_fname)
    cmd.reinitialize()
    cmd.load(mol2_fname)
    cmd.save(str(new_sdf_fname))
    return new_sdf_fname

Making pwd redundant

I’m going to keep this one brief, because I am mid-confirmation-and-paper-writing madness. I have seen too many people – both beginners and seasoned veterans – wandering around their Linux filesystem blindfolded:

Isn’t it hideous?

Whenever you want to see where you are, you have to execute pwd (present working directory), which will print your absolute location to stdout. If you have many terminals open at the same time, it is easy to lose track of where you are, and every other command becomes pwd; surely, I hear you cry, there has to be a better way!

Well, fear not! With a little tinkering with ~/.bashrc, we can display the working directory as part of the special PS1 environment variable, responsible for how your username and computer are displayed above. Putting the following at the top of ~/.bashrc

me=`id | awk -F\( '{print $2}' | awk -F\) '{print $1}'`
export PS1="`uname -n |  /bin/sed 's/\..*//'`{$me}:\$PWD$ "

… saving, and starting a new termanal window results in:

Much better!

I haven’t used pwd in 3 years.

Non-linear Dependence? Mutual Information to the Rescue!

We are all familiar with the idea of a correlation. In the broadest sense of the word, a correlation can refer to any kind of dependence between two variables. There are three widely used tests for correlation:

  • Spearman’s r: Used to measure a linear relationship between two variables. Requires linear dependence and each marginal distribution to be normal.
  • Pearson’s ρ: Used to measure rank correlations. Requires the dependence structure to be described by a monotonic relationship
  • Kendall’s 𝛕: Used to measure ordinal association between variables.

While these three measures give us plenty of options to work with, they do not work in all cases. Take for example the following variables, Y1 and Y2. These might be two variables that vary in a concerted manner.

Perhaps we suspect that a state change in Y1 leads to a state change in Y2 or vice versa and we want to measure the association between these variables. Using the three measures of correlation, we get the following results:

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How to Blopig

Blopig has a wealth of knowledge, with everything from a Bayesian answer to the question “should ketchup be stored in the fridge?“* to the Nobel-Prize-Winner-approved analysis of AlphaFold2. Blopig runs on WordPress and uses blocks, components for adding different types of content to a post. These are blocks like paragraphs, headers, images, image galleries, and videos. Here are some hints and tips for getting the most out of WordPress.

One of the first blocks worth mentioning is the “Read More…” block…

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