Alistair's Lab Notebook

10:00 am – 2:45 am

Chromatin

Literature

• reading Mirny 2011 review

Simulations

Data for Bogdan

• send volume table to Bodgan to explore densities
• send table of internal volumes
• send table of intact Rgs
• send table of internal Rgs

To plot for XZ meeting

• blue internal scaling, just BX-C data. With .5 and .33 reference lines
• blue internal scaling, just ANT-C data. With .5 and .33 reference lines
• simulation of pure black chromatin.

Simulations

• got black working
• added yellow – too many holes? allows black to equilibrate?
• reduced yellow – seems to help, hard to tell when not a lot of yellow to go by.
• went back to all black – back to 0.4 scaling?
• went back to all black with Grosberg repulsion, still 0.4 scaling.
• reduced number of domains and increased min domain size (maybe the too smalls are getting in the way).
• this fixes things, back to 0.3. ‘YellowBlackAllK4_Rnd’
• switching back from Grosberg to tagged force. Seems to be okay. 0.32 ‘YellowBlackAllK5_Rnd’
• adding back 10% yellow ‘YellowBlackAllK6_Rnd’. Black seems to stay down at 0.3 to 0.35, though the data is supernoisy with this few points. Yellow with 3 points is useless to fit. showing 0.24 (-1,1.5)
• ‘YellowBlackAllK7_Rnd’ with more yellow poitns is still pretty even (0.32 black [.21 .42], 0.26 yellow [.13 .4])
• let’s try making yellow a bit more phantom than 5:50. ‘YellowBlackAllK8_Rnd’ looking at 2::50 comparison
• This looks a bit more promising, black is staying at .3, yellow is occassionally climbing above (though still very noise).
• running 200 step, more subchains, larger polymer, long run overnight ‘YellowBlackAllK11_Rnd’.
• overnight run looks decent. data is still very noisy, maybe this will average away if we use a random chain configuration to start instead of the deterministic wrapping, and we do we enough repeats. (current system of repeats doesn’t average away noise).

Project 2

• restart Cajal running on scans

11:00 am – 11:00 pm

Computation

• investigate local data running on Odyssey CPU
• does not look straight-forward. Writing to RChelp for more info

Project 2

• run threshold scans on Cajal — now going on original test dataset and new dataset

Chromatin

• new simulation, stiffer blue, shorter run time, less chain crossing
• black chromatin still gets around

10:00 am – 8:00 pm

Modeling Calculations

fractions of chromatin types in genome

• of the 120 Mb of classified sequence (some 60 Mb ‘other’ class)
• estimate: from Pc track, 1 – 3% ‘Blue’
• estimate: from yellow/red Filion data: 34% ‘Yellow’ (21% ‘Yellow’,13% ‘Red’).
• estimate: from black and blue minus true blue: 64% ‘Black’

estimate monomer length and size

I estimate the intersection of three scaling laws to occur between 0.4 kb and 3.2 kb to ~95% confidence*.

*About the calculation:
I have 3 lines from our 3 scaling laws. Around each line I can plot the lower and upper uncertainty bounds and turn each line into a pair of lower and upper extema. If I compute the first time the lower extrema of the yellow crosses the upper extrema of the blue I call that the largest value possible for the intersection. But I think its wrong to compute this using the 95% bounds, because the probability all 3 of these datasets are at or outside their 95% limit is (0.05)^3 not (0.05). So instead I use the 63% bounds around the line and compute the earliest (and latest) time where they could all intersect and I get the above numbers.

The volume of the chromatin at the crossing point depends a little which crossing point in this range we look at.

• at 0.4 kb it ranges from 10^5.4 to 10^5.8 nm
• at 1 kb it ranges from 10^5.8 to 10^6.1 nm
• at 3.2 kb it ranges from 10^6.3 10^6.7 nm
  based on the the confidence intervals.

Any one of the monomer lengths (0.4 to 3.2) can satisfy the constraint that the biggest blue has a volume fraction less than 1.0 if we chose its lower bound for the the monomer volume estimate. (the upper estimates all put the volume fraction way above 1).

Modeling to do

• check convergence time:
  • run mulitple very long simulations, see how Rg changes at several subchain lengths for blue, black and yellow.
• formalize computation of monomer size. Done. See above.

9:45 am – 12:15 am

Project 2

• see post

Chromatin

Openmm configuration

• updated openmm-polymer in Python26/Lib/site-packages/ to latest download
• archived old openmm-polymer in Research/Software/OpenMMchromatin/Archive (this had some of my scripts as well)
• reorganizing OpenMMchromatin into
  • Archive
  • Templates
  • Simulations
  • Functions
  • Scratch

Coding with Bogdan

• Realization: should only look at scaling much shorter than constrained volume traversal.
  • the flat scaling in fractal globules is just after the polymer reaches the boundaries of confinement
  • sticky polymers set their own boundaries based on the size of the ball in which the nodes of the polymer still have sufficient contact.
• implemented variable stiffness simulation
• implemented variable stickiness simulation

Chromatin simulation results

• see post

10:00 am – 12:15 am

Project 2

• see post.

Chromatin

• heard back from Geoff
• got example code of fractal globule, need to run and test

Computer

• sent quote request to Dell
• discussed pricing with Matt
• discussed quote request with PCSFE

10:00 am – 11:00 pm

Project 2

• debugging code
• sub-group meeting
• see this post on initial threshold scanning work
• and this post
• and this post on to do summary.

Chromatin Project

• email Geoff for update / black chromatin model
• send confined polymer code to Bogdan
• Working on draft.
• finished first pass through the Introduction
• working on
• email Bogdan about planning meetings with XZ.

Lab Network Stuff

• setup Ye on Cajal
• Tuck is out of memory. And somehow running Windows2012 server or 2008 remotely via an interactive desktop run by Shu? This block local access at the terminal.
• Sent request to PCSFE for quote.
• Dell PowerEdge T630 2x 10 Core 2.3 GHz processors (40 threads) + 4×16 GB RAM (expandable to 24X. 4,612)