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Revision: 62
Committed: Tue Aug 6 22:06:13 2002 UTC (22 years, 1 month ago) by mmeineke
Content type: application/x-tex
File size: 10054 byte(s)
Log Message:

added a crapload of crap that may or may norbe neccassary. Time will tell. Also, got footnote references working.

File Contents

# User Rev Content
1 mmeineke 49 % temporary preamble
2    
3 mmeineke 54 %\documentclass[ps,frames,final,nototal,slideColor,colorBG]{prosper}
4    
5 mmeineke 49 \documentclass{seminar}
6 mmeineke 52 \usepackage{color}
7 mmeineke 54
8 mmeineke 49 \usepackage{amsmath}
9 mmeineke 52 \usepackage{amssymb}
10 mmeineke 62 \usepackage{wrapfig}
11 mmeineke 49 \usepackage{epsf}
12 mmeineke 62 \usepackage{jurabib}
13 mmeineke 49
14     % ----------------------
15     % | Title |
16     % ----------------------
17    
18 mmeineke 62 \title{A Mezzoscale Model for Phospholipid MD Simulations}
19 mmeineke 49
20     \author{Matthew A. Meineke\\
21     Department of Chemistry and Biochemistry\\
22     University of Notre Dame\\
23     Notre Dame, Indiana 46556}
24    
25     \date{\today}
26    
27     %-------------------------------------------------------------------
28     % Begin Document
29    
30     \begin{document}
31 mmeineke 62
32 mmeineke 49 \maketitle
33    
34 mmeineke 62 \bibliography{canidacy_slides}
35     \bibliographystyle{jurabib}
36 mmeineke 49
37    
38 mmeineke 62
39    
40    
41 mmeineke 49 % Slide 1
42     \begin{slide} {Talk Outline}
43     \begin{itemize}
44    
45     \item Discussion of the research motivation and goals
46    
47     \item Methodology
48    
49     \item Discussion of current research and preliminary results
50    
51     \item Future research
52    
53     \end{itemize}
54     \end{slide}
55    
56    
57     % Slide 2
58    
59 mmeineke 62 \begin{slide}{Motivation A: Long Length Scales}
60    
61    
62    
63     \begin{wrapfigure}{r}{45mm}
64    
65     \epsfxsize=45mm
66     \epsfbox{ripple.epsi}
67    
68     \end{wrapfigure}
69    
70     Ripple phase:
71    
72     \begin{itemize}
73    
74     \item
75     The ripple (~$P_{\beta'}$~) phase lies in the transition from the gel
76     to fluid phase.
77    
78     \item
79     periodicity of 100 - 200 $\mbox{\AA}$\footcite{Berne90}
80    
81     \end{itemize}
82     \end{slide}
83    
84    
85    
86    
87    
88    
89 mmeineke 49 \begin{slide}{Motivation}
90 mmeineke 54
91     There is a strong need in phospholipid bilayer simulations for the
92     capability to simulate both long time and length scales. Consider the
93     following:
94    
95 mmeineke 49 \begin{itemize}
96    
97     \item Drug diffusion
98 mmeineke 54 \begin{itemize}
99     \item Some drug molecules may spend an appreciable time in the
100     membrane. Long time scale dynamics are needed to observe and
101     characterize their actions.
102     \end{itemize}
103 mmeineke 49
104 mmeineke 54 \item Ripple phase
105     \begin{itemize}
106     \item Between the bilayer gel and fluid phase there exists a ripple
107     phase. This phase has a period of about 100 - 200 $\mbox{\AA}$.
108     \end{itemize}
109 mmeineke 49
110 mmeineke 54 \item Bilayer formation dynamics
111     \begin{itemize}
112     \item Initial simulations show that bilayers can take upwards of
113     20 ns to form completely.
114     \end{itemize}
115 mmeineke 49
116     \end{itemize}
117     \end{slide}
118    
119    
120     % Slide 4
121    
122     \begin{slide}{Length Scale Simplification}
123     \begin{itemize}
124    
125     \item
126     Replace any charged interactions of the system with dipoles.
127    
128     \begin{itemize}
129 mmeineke 53 \item Allows for computational scaling approximately by $N$ for
130 mmeineke 49 dipole-dipole interactions.
131 mmeineke 53 \item In contrast, the Ewald sum scales approximately by $N \log N$.
132 mmeineke 49 \end{itemize}
133    
134     \item
135     Use unified models for the water and the lipid chain.
136    
137     \begin{itemize}
138     \item Drastically reduces the number of atoms to simulate.
139     \item Number of water interactions alone reduced by $\frac{1}{3}$.
140     \end{itemize}
141     \end{itemize}
142     \end{slide}
143    
144    
145     % Slide 5
146    
147     \begin{slide}{Time Scale Simplification}
148     \begin{itemize}
149    
150     \item
151     No explicit hydrogens
152    
153     \begin{itemize}
154     \item Hydrogen bond vibration is normally one of the fastest time
155     events in a simulation.
156     \end{itemize}
157    
158     \item
159     Constrain all bonds to be of fixed length.
160    
161     \begin{itemize}
162 mmeineke 53 \item As with the hydrogens, bond vibrations are the fastest motion in
163     a simulation
164 mmeineke 49 \end{itemize}
165    
166     \item
167     Allows time steps of up to 3 fs with the current integrator.
168    
169     \end{itemize}
170     \end{slide}
171    
172    
173     % Slide 6
174     \begin{slide}{Molecular Dynamics}
175    
176 mmeineke 53 All of our simulations will be carried out using molecular
177     dynamics. This involves solving Newton's equations of motion using
178 mmeineke 49 the classical \emph{Hamiltonian} as follows:
179    
180     \begin{equation}
181     H(\vec{q},\vec{p}) = T(\vec{p}) + V(\vec{q})
182     \end{equation}
183    
184     Here $T(\vec{p})$ is the kinetic energy of the system which is a
185 mmeineke 53 function of momentum. In Cartesian space, $T(\vec{p})$ can be
186 mmeineke 49 written as:
187    
188     \begin{equation}
189     T(\vec{p}) = \sum_{i=1}^{N} \sum_{\alpha = x,y,z} \frac{p^{2}_{i\alpha}}{2m_{i}}
190     \end{equation}
191    
192     \end{slide}
193    
194    
195     % Slide 7
196     \begin{slide}{The Potential}
197    
198     The main part of the simulation is then the calculation of forces from
199     the potential energy.
200    
201     \begin{equation}
202     \vec{F}(\vec{q}) = - \nabla V(\vec{q})
203     \end{equation}
204    
205     The potential itself is made of several parts.
206    
207     \begin{equation}
208     V_{tot} =
209     \overbrace{V_{l} + V_{\theta} + V_{\omega}}^{\mbox{bonded}} +
210     \overbrace{V_{l\!j} + V_{d\!p} + V_{s\!s\!d}}^{\mbox{non-bonded}}
211     \end{equation}
212    
213     Where the bond interactions $V_{l}$, $V_{\theta}$, and $V_{\omega}$ are
214     the bond, bend, and torsion potentials, and the non-bonded
215 mmeineke 51 interactions $V_{l\!j}$, $V_{d\!p}$, and $V_{s\!p}$ are the
216     lenard-jones, dipole-dipole, and sticky potential interactions.
217 mmeineke 49
218     \end{slide}
219    
220    
221 mmeineke 51 % Slide 8
222 mmeineke 49
223 mmeineke 51 \begin{slide}{Soft Sticky Dipole Model}
224 mmeineke 49
225 mmeineke 52 The Soft-Sticky model for water is a reduced model.
226 mmeineke 49
227 mmeineke 52 \begin{itemize}
228 mmeineke 49
229 mmeineke 52 \item
230     The model is represented by a single point mass at the water's center
231     of mass.
232 mmeineke 49
233 mmeineke 52 \item
234     The point mass contains a fixed dipole of 2.35 D pointing from the
235 mmeineke 53 oxygens toward the hydrogens.
236 mmeineke 51
237 mmeineke 52 \end{itemize}
238 mmeineke 51
239 mmeineke 52 It's potential is as follows:
240    
241     \begin{equation}
242     V_{s\!s\!d} = V_{l\!j}(r_{i\!j}) + V_{d\!p}(r_{i\!j},\Omega_{i},\Omega_{j})
243     + V_{s\!p}(r_{i\!j},\Omega_{i},\Omega_{j})
244     \end{equation}
245     \end{slide}
246    
247 mmeineke 54 % Slide 8b
248 mmeineke 52
249 mmeineke 54 \begin{slide}{SSD Diagram}
250    
251     \begin{center}
252     \begin{figure}
253     \epsfxsize=50mm
254     \epsfbox{ssd.epsi}
255     \end{figure}
256     \end{center}
257    
258     A Diagram of the SSD model.
259     \end{slide}
260    
261 mmeineke 52 % Slide 9
262     \begin{slide}{Hydrogen Bonding in SSD}
263    
264     It is important to note that SSD has a potential specifically to
265 mmeineke 53 recreate the hydrogen bonding network of water.
266 mmeineke 52
267 mmeineke 54
268 mmeineke 52 ICE SSD
269    
270     ICE point Dipole
271    
272 mmeineke 54
273 mmeineke 53 The importance of the hydrogen bond network is it's significant
274 mmeineke 52 contribution to the hydrophobic driving force of bilayer formation.
275     \end{slide}
276    
277    
278     % Slide 10
279    
280     \begin{slide}{The Lipid Model}
281    
282 mmeineke 53 To eliminate the need for charge-charge interactions, our lipid model
283     replaces the phospholipid head group with a single large head group
284     atom containing a freely oriented dipole. The tail is a simple alkane chain.
285    
286     Lipid Properties:
287     \begin{itemize}
288     \item $|\vec{\mu}_{\text{HEAD}}| = 20.6\ \text{D}$
289     \item $m_{\text{HEAD}} = 196\ \text{amu}$
290     \item Tail atoms are unified CH, $\text{CH}_2$, and $\text{CH}_3$ atoms
291     \begin{itemize}
292     \item Alkane forcefield parameters taken from TraPPE
293     \end{itemize}
294     \end{itemize}
295    
296     \end{slide}
297    
298    
299     % Slide 11
300    
301     \begin{slide}{Lipid Model}
302    
303 mmeineke 52
304 mmeineke 54
305 mmeineke 52 \end{slide}
306    
307    
308 mmeineke 53 % Slide 12
309 mmeineke 52
310     \begin{slide}{Initial Runs: 25 Lipids in water}
311    
312 mmeineke 53 \textbf{Simulation Parameters:}
313 mmeineke 52
314 mmeineke 53 \begin{itemize}
315    
316     \item Starting Configuration:
317     \begin{itemize}
318     \item 25 lipid molecules arranged in a 5 x 5 square
319     \item square was surrounded by a sea of 1386 waters
320     \begin{itemize}
321     \item final water to lipid ratio was 55.4:1
322     \end{itemize}
323     \end{itemize}
324    
325     \item Lipid had only a single saturated chain of 16 carbons
326    
327     \item Box Size: 34.5 $\mbox{\AA}$ x 39.4 $\mbox{\AA}$ x 39.4 $\mbox{\AA}$
328    
329     \item dt = 2.0 - 3.0 fs
330    
331     \item T = 300 K
332    
333     \item NVE ensemble
334    
335     \item Periodic boundary conditions
336     \end{itemize}
337    
338 mmeineke 52 \end{slide}
339    
340    
341 mmeineke 53 % Slide 13
342 mmeineke 52
343 mmeineke 54 \begin{slide}{5x5: Initial}
344 mmeineke 52
345 mmeineke 54 \begin{center}
346     \begin{figure}
347     \epsfxsize=50mm
348     \epsfbox{5x5-initial.eps}
349     \end{figure}
350     \end{center}
351 mmeineke 52
352 mmeineke 54 The initial configuration
353 mmeineke 52
354     \end{slide}
355    
356 mmeineke 54 \begin{slide}{5x5: Final}
357 mmeineke 52
358 mmeineke 54 \begin{center}
359     \begin{figure}
360     \epsfxsize=60mm
361     \epsfbox{5x5-1.7ns.eps}
362     \end{figure}
363     \end{center}
364    
365     The final configuration at 1.7 ns.
366    
367     \end{slide}
368    
369    
370 mmeineke 53 % Slide 14
371 mmeineke 52
372     \begin{slide}{5x5: $g(r)$}
373    
374 mmeineke 54 \begin{center}
375     \begin{figure}
376     \epsfxsize=60mm
377     \epsfbox{all5x5-HEAD-HEAD-gr.eps}
378     \end{figure}
379     \end{center}
380 mmeineke 52
381    
382 mmeineke 54 \end{slide}
383 mmeineke 52
384 mmeineke 54 \begin{slide}{5x5: $g(r)$}
385    
386     \begin{center}
387     \begin{figure}
388     \epsfxsize=60mm
389     \epsfbox{all5x5-HEAD-X-gr.eps}
390     \end{figure}
391     \end{center}
392    
393    
394 mmeineke 52 \end{slide}
395    
396    
397 mmeineke 53 % Slide 15
398 mmeineke 52
399     \begin{slide}{5x5: $\cos$ correlations}
400    
401 mmeineke 54 \begin{center}
402     \begin{figure}
403     \epsfxsize=60mm
404     \epsfbox{all5x5-HEAD-HEAD-cr.eps}
405     \end{figure}
406     \end{center}
407 mmeineke 52
408     \end{slide}
409    
410 mmeineke 54 \begin{slide}{5x5: $\cos$ correlations}
411 mmeineke 52
412 mmeineke 54 \begin{center}
413     \begin{figure}
414     \epsfxsize=60mm
415     \epsfbox{all5x5-HEAD-X-cr.eps}
416     \end{figure}
417     \end{center}
418    
419     \end{slide}
420    
421    
422 mmeineke 53 % Slide 16
423 mmeineke 52
424 mmeineke 53 \begin{slide}{Initial Runs: 50 Lipids randomly arranged in water}
425 mmeineke 52
426 mmeineke 53 \textbf{Simulation Parameters:}
427 mmeineke 52
428 mmeineke 53 \begin{itemize}
429    
430     \item Starting Configuration:
431     \begin{itemize}
432     \item 50 lipid molecules arranged randomly in a rectangular box
433     \item The box was then filled with 1384 waters
434     \begin{itemize}
435     \item final water to lipid ratio was 27:1
436     \end{itemize}
437     \end{itemize}
438    
439     \item Lipid had only a single saturated chain of 16 carbons
440    
441     \item Box Size: 26.6 $\mbox{\AA}$ x 26.6 $\mbox{\AA}$ x 108.4 $\mbox{\AA}$
442    
443     \item dt = 2.0 - 3.0 fs
444    
445     \item T = 300 K
446    
447     \item NVE ensemble
448    
449     \item Periodic boundary conditions
450    
451     \end{itemize}
452    
453 mmeineke 52 \end{slide}
454    
455    
456 mmeineke 53 % Slide 17
457 mmeineke 52
458 mmeineke 54 \begin{slide}{R-50: Initial}
459 mmeineke 52
460 mmeineke 54 \begin{center}
461     \begin{figure}
462     \epsfxsize=100mm
463     \epsfbox{r50-initial.eps}
464     \end{figure}
465     \end{center}
466 mmeineke 52
467 mmeineke 54 The initial configuration
468 mmeineke 52
469     \end{slide}
470    
471 mmeineke 54 \begin{slide}{R-50: Final}
472 mmeineke 52
473 mmeineke 54 \begin{center}
474     \begin{figure}
475     \epsfxsize=100mm
476     \epsfbox{r50-521ps.eps}
477     \end{figure}
478     \end{center}
479    
480     The fianl configuration at 521 ps
481    
482     \end{slide}
483    
484    
485 mmeineke 53 % Slide 18
486 mmeineke 52
487     \begin{slide}{R-50: $g(r)$}
488    
489    
490 mmeineke 54 \begin{center}
491     \begin{figure}
492     \epsfxsize=60mm
493     \epsfbox{r50-HEAD-HEAD-gr.eps}
494     \end{figure}
495     \end{center}
496 mmeineke 52
497 mmeineke 54 \end{slide}
498 mmeineke 52
499 mmeineke 54
500     \begin{slide}{R-50: $g(r)$}
501    
502    
503     \begin{center}
504     \begin{figure}
505     \epsfxsize=60mm
506     \epsfbox{r50-HEAD-X-gr.eps}
507     \end{figure}
508     \end{center}
509    
510 mmeineke 52 \end{slide}
511    
512    
513 mmeineke 53 % Slide 19
514 mmeineke 52
515     \begin{slide}{R-50: $\cos$ correlations}
516    
517    
518 mmeineke 54 \begin{center}
519     \begin{figure}
520     \epsfxsize=60mm
521     \epsfbox{r50-HEAD-HEAD-cr.eps}
522     \end{figure}
523     \end{center}
524    
525 mmeineke 52 \end{slide}
526    
527 mmeineke 54 \begin{slide}{R-50: $\cos$ correlations}
528 mmeineke 52
529 mmeineke 54
530     \begin{center}
531     \begin{figure}
532     \epsfxsize=60mm
533     \epsfbox{r50-HEAD-X-cr.eps}
534     \end{figure}
535     \end{center}
536    
537     \end{slide}
538    
539    
540 mmeineke 53 % Slide 20
541 mmeineke 52
542     \begin{slide}{Future Directions}
543    
544 mmeineke 53 \begin{itemize}
545 mmeineke 52
546 mmeineke 53 \item
547     Simulation of a lipid with 2 chains, or perhaps expand the current
548     unified chain atoms to take up greater steric bulk.
549    
550     \item
551     Incorporate constant pressure and constant temperature into the ensemble.
552    
553     \item
554     Parrellize the code.
555    
556     \end{itemize}
557 mmeineke 52 \end{slide}
558    
559    
560 mmeineke 53 % Slide 21
561 mmeineke 52
562     \begin{slide}{Acknowledgements}
563    
564 mmeineke 53 \begin{itemize}
565 mmeineke 52
566 mmeineke 53 \item Dr. J. Daniel Gezelter
567     \item Christopher Fennel
568     \item Charles Vardeman
569     \item Teng Lin
570 mmeineke 52
571 mmeineke 53 \end{itemize}
572    
573     Funding by:
574     \begin{itemize}
575     \item Dreyfus New Faculty Award
576     \end{itemize}
577    
578 mmeineke 52 \end{slide}
579    
580    
581    
582    
583    
584    
585    
586    
587 mmeineke 49 %%%%%%%%%%%%%%%%%%%%%%%%%% END %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
588    
589     \end{document}