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Revision: 63
Committed: Wed Aug 7 19:09:03 2002 UTC (22 years, 8 months ago) by mmeineke
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File size: 15099 byte(s)
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switched in Chuck's magic slide enviroment

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# Content
1 % temporary preamble
2
3 %\documentclass[ps,frames,final,nototal,slideColor,colorBG]{prosper}
4
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10 \usepackage{amsmath}
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124 \textcolor{Blue2}{~~University of Notre Dame~~}}%
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127 \lower.22ex\hbox{%
128 \textcolor{SaddleBrown}{~~Matthew Meineke~~}}%
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150 grestore} def end
151 }
152
153 % And here we are...
154
155 \setcounter{slide}{-1}
156 %\includeonly{slide10}
157
158
159
160
161
162
163 % ----------------------
164 % | Title |
165 % ----------------------
166
167 \title{A Mezzoscale Model for Phospholipid MD Simulations}
168
169 \author{Matthew A. Meineke\\
170 Department of Chemistry and Biochemistry\\
171 University of Notre Dame\\
172 Notre Dame, Indiana 46556}
173
174 \date{\today}
175
176 %-------------------------------------------------------------------
177 % Begin Document
178
179 \begin{document}
180
181 %\maketitle
182
183
184
185
186
187 \nobibliography{canidacy_slides}
188 \bibliographystyle{jurabib}
189
190
191 % Slide 0 Title slide
192 \begin{slide}
193 \begin{center}
194 \bfseries
195 \fontsize{24pt}{30pt}\selectfont \color{Black}
196 A Mezzoscale Model for Phospholipid MD Simulations \par
197 \fontsize{16pt}{20pt}\selectfont \color{Green3}
198 Matthew A. Meineke\par
199 \fontsize{12pt}{15pt}\selectfont \color{Purple2}
200 Department of Chemistry and Biochemisty \par
201 University of Notre Dame \par
202 Notre Dame, IN 46556 \par
203 \fontsize{12pt}{15pt}\selectfont \color{Red} \date{today} \par
204 \end{center}
205 \end{slide}
206
207 % Slide 1
208 \begin{slide} {Talk Outline}
209 \begin{itemize}
210
211 \item Discussion of the research motivation and goals
212
213 \item Methodology
214
215 \item Discussion of current research and preliminary results
216
217 \item Future research
218
219 \end{itemize}
220 \end{slide}
221
222
223 % Slide 2
224
225 \begin{slide}
226
227 \centerline{\LARGE Motivation A:
228 Long Length Scales}
229 \begin{wrapfigure}{r}{60mm}
230
231 \epsfxsize=45mm
232 \epsfbox{ripple.epsi}
233
234 \end{wrapfigure}
235
236
237
238
239 %\epsfbox{ripple.epsi}
240 %\begin{floatingfigure}{0.45\linewidth}
241 % \incffig{ripple.epsi}
242 %\end{floatingfigure}
243
244
245
246 \mbox{}
247 Ripple phase:
248 \begin{itemize}
249
250 \item
251 The ripple (~$P_{\beta'}$~) phase lies in the transition from the gel
252 to fluid phase.
253
254 \item
255 Periodicity of 100 - 200 $\mbox{\AA}$\footcite{Berne90}
256
257 \end{itemize}
258 \vspace{30mm}
259 \end{slide}
260
261
262
263
264
265
266 \begin{slide}{Motivation}
267
268 There is a strong need in phospholipid bilayer simulations for the
269 capability to simulate both long time and length scales. Consider the
270 following:
271
272 \begin{itemize}
273
274 \item Drug diffusion
275 \begin{itemize}
276 \item Some drug molecules may spend an appreciable time in the
277 membrane. Long time scale dynamics are needed to observe and
278 characterize their actions.
279 \end{itemize}
280
281 \item Ripple phase
282 \begin{itemize}
283 \item Between the bilayer gel and fluid phase there exists a ripple
284 phase. This phase has a period of about 100 - 200 $\mbox{\AA}$.
285 \end{itemize}
286
287 \item Bilayer formation dynamics
288 \begin{itemize}
289 \item Initial simulations show that bilayers can take upwards of
290 20 ns to form completely.
291 \end{itemize}
292
293 \end{itemize}
294 \end{slide}
295
296
297 % Slide 4
298
299 \begin{slide}{Length Scale Simplification}
300 \begin{itemize}
301
302 \item
303 Replace any charged interactions of the system with dipoles.
304
305 \begin{itemize}
306 \item Allows for computational scaling approximately by $N$ for
307 dipole-dipole interactions.
308 \item In contrast, the Ewald sum scales approximately by $N \log N$.
309 \end{itemize}
310
311 \item
312 Use unified models for the water and the lipid chain.
313
314 \begin{itemize}
315 \item Drastically reduces the number of atoms to simulate.
316 \item Number of water interactions alone reduced by $\frac{1}{3}$.
317 \end{itemize}
318 \end{itemize}
319 \end{slide}
320
321
322 % Slide 5
323
324 \begin{slide}{Time Scale Simplification}
325 \begin{itemize}
326
327 \item
328 No explicit hydrogens
329
330 \begin{itemize}
331 \item Hydrogen bond vibration is normally one of the fastest time
332 events in a simulation.
333 \end{itemize}
334
335 \item
336 Constrain all bonds to be of fixed length.
337
338 \begin{itemize}
339 \item As with the hydrogens, bond vibrations are the fastest motion in
340 a simulation
341 \end{itemize}
342
343 \item
344 Allows time steps of up to 3 fs with the current integrator.
345
346 \end{itemize}
347 \end{slide}
348
349
350 % Slide 6
351 \begin{slide}{Molecular Dynamics}
352
353 All of our simulations will be carried out using molecular
354 dynamics. This involves solving Newton's equations of motion using
355 the classical \emph{Hamiltonian} as follows:
356
357 \begin{equation}
358 H(\vec{q},\vec{p}) = T(\vec{p}) + V(\vec{q})
359 \end{equation}
360
361 Here $T(\vec{p})$ is the kinetic energy of the system which is a
362 function of momentum. In Cartesian space, $T(\vec{p})$ can be
363 written as:
364
365 \begin{equation}
366 T(\vec{p}) = \sum_{i=1}^{N} \sum_{\alpha = x,y,z} \frac{p^{2}_{i\alpha}}{2m_{i}}
367 \end{equation}
368
369 \end{slide}
370
371
372 % Slide 7
373 \begin{slide}{The Potential}
374
375 The main part of the simulation is then the calculation of forces from
376 the potential energy.
377
378 \begin{equation}
379 \vec{F}(\vec{q}) = - \nabla V(\vec{q})
380 \end{equation}
381
382 The potential itself is made of several parts.
383
384 \begin{equation}
385 V_{tot} =
386 \overbrace{V_{l} + V_{\theta} + V_{\omega}}^{\mbox{bonded}} +
387 \overbrace{V_{l\!j} + V_{d\!p} + V_{s\!s\!d}}^{\mbox{non-bonded}}
388 \end{equation}
389
390 Where the bond interactions $V_{l}$, $V_{\theta}$, and $V_{\omega}$ are
391 the bond, bend, and torsion potentials, and the non-bonded
392 interactions $V_{l\!j}$, $V_{d\!p}$, and $V_{s\!p}$ are the
393 lenard-jones, dipole-dipole, and sticky potential interactions.
394
395 \end{slide}
396
397
398 % Slide 8
399
400 \begin{slide}{Soft Sticky Dipole Model}
401
402 The Soft-Sticky model for water is a reduced model.
403
404 \begin{itemize}
405
406 \item
407 The model is represented by a single point mass at the water's center
408 of mass.
409
410 \item
411 The point mass contains a fixed dipole of 2.35 D pointing from the
412 oxygens toward the hydrogens.
413
414 \end{itemize}
415
416 It's potential is as follows:
417
418 \begin{equation}
419 V_{s\!s\!d} = V_{l\!j}(r_{i\!j}) + V_{d\!p}(r_{i\!j},\Omega_{i},\Omega_{j})
420 + V_{s\!p}(r_{i\!j},\Omega_{i},\Omega_{j})
421 \end{equation}
422 \end{slide}
423
424 % Slide 8b
425
426 \begin{slide}{SSD Diagram}
427
428 \begin{center}
429 \begin{figure}
430 \epsfxsize=50mm
431 \epsfbox{ssd.epsi}
432 \end{figure}
433 \end{center}
434
435 A Diagram of the SSD model.
436 \end{slide}
437
438 % Slide 9
439 \begin{slide}{Hydrogen Bonding in SSD}
440
441 It is important to note that SSD has a potential specifically to
442 recreate the hydrogen bonding network of water.
443
444
445 ICE SSD
446
447 ICE point Dipole
448
449
450 The importance of the hydrogen bond network is it's significant
451 contribution to the hydrophobic driving force of bilayer formation.
452 \end{slide}
453
454
455 % Slide 10
456
457 \begin{slide}{The Lipid Model}
458
459 To eliminate the need for charge-charge interactions, our lipid model
460 replaces the phospholipid head group with a single large head group
461 atom containing a freely oriented dipole. The tail is a simple alkane chain.
462
463 Lipid Properties:
464 \begin{itemize}
465 \item $|\vec{\mu}_{\text{HEAD}}| = 20.6\ \text{D}$
466 \item $m_{\text{HEAD}} = 196\ \text{amu}$
467 \item Tail atoms are unified CH, $\text{CH}_2$, and $\text{CH}_3$ atoms
468 \begin{itemize}
469 \item Alkane forcefield parameters taken from TraPPE
470 \end{itemize}
471 \end{itemize}
472
473 \end{slide}
474
475
476 % Slide 11
477
478 \begin{slide}{Lipid Model}
479
480
481
482 \end{slide}
483
484
485 % Slide 12
486
487 \begin{slide}{Initial Runs: 25 Lipids in water}
488
489 \textbf{Simulation Parameters:}
490
491 \begin{itemize}
492
493 \item Starting Configuration:
494 \begin{itemize}
495 \item 25 lipid molecules arranged in a 5 x 5 square
496 \item square was surrounded by a sea of 1386 waters
497 \begin{itemize}
498 \item final water to lipid ratio was 55.4:1
499 \end{itemize}
500 \end{itemize}
501
502 \item Lipid had only a single saturated chain of 16 carbons
503
504 \item Box Size: 34.5 $\mbox{\AA}$ x 39.4 $\mbox{\AA}$ x 39.4 $\mbox{\AA}$
505
506 \item dt = 2.0 - 3.0 fs
507
508 \item T = 300 K
509
510 \item NVE ensemble
511
512 \item Periodic boundary conditions
513 \end{itemize}
514
515 \end{slide}
516
517
518 % Slide 13
519
520 \begin{slide}{5x5: Initial}
521
522 \begin{center}
523 \begin{figure}
524 \epsfxsize=50mm
525 \epsfbox{5x5-initial.eps}
526 \end{figure}
527 \end{center}
528
529 The initial configuration
530
531 \end{slide}
532
533 \begin{slide}{5x5: Final}
534
535 \begin{center}
536 \begin{figure}
537 \epsfxsize=60mm
538 \epsfbox{5x5-1.7ns.eps}
539 \end{figure}
540 \end{center}
541
542 The final configuration at 1.7 ns.
543
544 \end{slide}
545
546
547 % Slide 14
548
549 \begin{slide}{5x5: $g(r)$}
550
551 \begin{center}
552 \begin{figure}
553 \epsfxsize=60mm
554 \epsfbox{all5x5-HEAD-HEAD-gr.eps}
555 \end{figure}
556 \end{center}
557
558
559 \end{slide}
560
561 \begin{slide}{5x5: $g(r)$}
562
563 \begin{center}
564 \begin{figure}
565 \epsfxsize=60mm
566 \epsfbox{all5x5-HEAD-X-gr.eps}
567 \end{figure}
568 \end{center}
569
570
571 \end{slide}
572
573
574 % Slide 15
575
576 \begin{slide}{5x5: $\cos$ correlations}
577
578 \begin{center}
579 \begin{figure}
580 \epsfxsize=60mm
581 \epsfbox{all5x5-HEAD-HEAD-cr.eps}
582 \end{figure}
583 \end{center}
584
585 \end{slide}
586
587 \begin{slide}{5x5: $\cos$ correlations}
588
589 \begin{center}
590 \begin{figure}
591 \epsfxsize=60mm
592 \epsfbox{all5x5-HEAD-X-cr.eps}
593 \end{figure}
594 \end{center}
595
596 \end{slide}
597
598
599 % Slide 16
600
601 \begin{slide}{Initial Runs: 50 Lipids randomly arranged in water}
602
603 \textbf{Simulation Parameters:}
604
605 \begin{itemize}
606
607 \item Starting Configuration:
608 \begin{itemize}
609 \item 50 lipid molecules arranged randomly in a rectangular box
610 \item The box was then filled with 1384 waters
611 \begin{itemize}
612 \item final water to lipid ratio was 27:1
613 \end{itemize}
614 \end{itemize}
615
616 \item Lipid had only a single saturated chain of 16 carbons
617
618 \item Box Size: 26.6 $\mbox{\AA}$ x 26.6 $\mbox{\AA}$ x 108.4 $\mbox{\AA}$
619
620 \item dt = 2.0 - 3.0 fs
621
622 \item T = 300 K
623
624 \item NVE ensemble
625
626 \item Periodic boundary conditions
627
628 \end{itemize}
629
630 \end{slide}
631
632
633 % Slide 17
634
635 \begin{slide}{R-50: Initial}
636
637 \begin{center}
638 \begin{figure}
639 \epsfxsize=100mm
640 \epsfbox{r50-initial.eps}
641 \end{figure}
642 \end{center}
643
644 The initial configuration
645
646 \end{slide}
647
648 \begin{slide}{R-50: Final}
649
650 \begin{center}
651 \begin{figure}
652 \epsfxsize=100mm
653 \epsfbox{r50-521ps.eps}
654 \end{figure}
655 \end{center}
656
657 The fianl configuration at 521 ps
658
659 \end{slide}
660
661
662 % Slide 18
663
664 \begin{slide}{R-50: $g(r)$}
665
666
667 \begin{center}
668 \begin{figure}
669 \epsfxsize=60mm
670 \epsfbox{r50-HEAD-HEAD-gr.eps}
671 \end{figure}
672 \end{center}
673
674 \end{slide}
675
676
677 \begin{slide}{R-50: $g(r)$}
678
679
680 \begin{center}
681 \begin{figure}
682 \epsfxsize=60mm
683 \epsfbox{r50-HEAD-X-gr.eps}
684 \end{figure}
685 \end{center}
686
687 \end{slide}
688
689
690 % Slide 19
691
692 \begin{slide}{R-50: $\cos$ correlations}
693
694
695 \begin{center}
696 \begin{figure}
697 \epsfxsize=60mm
698 \epsfbox{r50-HEAD-HEAD-cr.eps}
699 \end{figure}
700 \end{center}
701
702 \end{slide}
703
704 \begin{slide}{R-50: $\cos$ correlations}
705
706
707 \begin{center}
708 \begin{figure}
709 \epsfxsize=60mm
710 \epsfbox{r50-HEAD-X-cr.eps}
711 \end{figure}
712 \end{center}
713
714 \end{slide}
715
716
717 % Slide 20
718
719 \begin{slide}{Future Directions}
720
721 \begin{itemize}
722
723 \item
724 Simulation of a lipid with 2 chains, or perhaps expand the current
725 unified chain atoms to take up greater steric bulk.
726
727 \item
728 Incorporate constant pressure and constant temperature into the ensemble.
729
730 \item
731 Parrellize the code.
732
733 \end{itemize}
734 \end{slide}
735
736
737 % Slide 21
738
739 \begin{slide}{Acknowledgements}
740
741 \begin{itemize}
742
743 \item Dr. J. Daniel Gezelter
744 \item Christopher Fennel
745 \item Charles Vardeman
746 \item Teng Lin
747
748 \end{itemize}
749
750 Funding by:
751 \begin{itemize}
752 \item Dreyfus New Faculty Award
753 \end{itemize}
754
755 \end{slide}
756
757
758
759
760
761
762
763
764 %%%%%%%%%%%%%%%%%%%%%%%%%% END %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
765
766 \end{document}