Molecular Modeling and Simulation: An Interdisciplinary Guide

Tamar Schlick

Textbook was prepared based on a course introduced at NYU and taught in the Fall of 1996 and in the Spring of 1999

Contents

Important Note: Chapters 1 and 2 were updated May 18, 2003! Remaining parts below correspond to published book.
Preface  (PDF)
Prelude  (PDF)
Table of Contents  (PDF)
1 Biomolecular Structure and Modeling: Historical Perspective   (PDF) - updated 5/18/03
1.1 A Multidisciplinary Enterprise
      1.1.1 Consilience
      1.1.2 What is Molecular Modeling
      1.1.3 Need For Critical Assessment
      1.1.4 Text Overview
1.2 Molecular Mechanics
      1.2.1 Pioneers
      1.2.2 Simulation Perspective
1.3 Experimental Progress
      1.3.1 Protein Crystallography
      1.3.2 DNA Structure
      1.3.3 Crystallography
      1.3.4 NMR Spectroscopy
1.4 Modern Era
      1.4.1 Biotechnology
      1.4.2 PCR and Beyond
1.5 Genome Sequencing
      1.5.1 Sequencing Overview
      1.5.2 Human Genome
Chapter 1 References (PDF)
2 Biomolecular Structure and Modeling: Problem and Application Perspective (PDF) - Updated 5/18/03
2.1 Computational Challenges
      2.1.1 Bioinformatics
      2.1.2 Structure From Sequence
2.2 Protein Folding
      2.2.1 Folding Views
      2.2.2 Folding Challenges
      2.2.3 Folding Simulations
      2.2.4 Chaperones
      2.2.5 Unstructured Proteins
2.3 Protein Misfolding
      2.3.1 Prions
      2.3.2 Infectious Proteins?
      2.3.3 Hypotheses
      2.3.4 Other Misfolding Processes
      2.3.5 Function From Structure
2.4 Practical Applications
      2.4.1 Drug Design
      2.4.2 AIDS Drugs
      2.4.3 Other Drugs
      2.4.4 A Long Way To Go
      2.4.5 Better Genes
      2.4.6 Designer Foods
      2.4.7 Designer Materials
      2.4.8 Cosmeceuticals
Chapter 2 References (PDF)
3 Protein Structure Introduction
3.1 Machinery of Life
      3.1.1 From Tissues to Hormones
      3.1.2 Size and Function Variability
      3.1.3 Chapter Overview
3.2 Amino Acid Building Blocks
      3.2.1 Basic C Unit
      3.2.2 Essential and Nonessential Amino Acids
      3.2.3 Linking Amino Acids
      3.2.4 The Amino Acid Repertoire
3.3 Sequence Variations in Proteins
      3.3.1 Globular Proteins
      3.3.2 Membrane and Fibrous Proteins
      3.3.3 Emerging Patterns from Genome Databases
      3.3.4 Sequence Similarity
3.4 Protein Conformation Framework
      3.4.1 The Flexible phi and psi and Rigid omega Dihedral Angles
      3.4.2 Rotameric Structures
      3.4.3 Ramachandran Plots
      3.4.4 Conformational Hierarchy
4 Protein Structure Hierarchy
4.1 Structure Hierarchy
4.2 Helices
      4.2.1 Classic - Helix
      4.2.2 310 and Helices
      4.2.3 Left - Handed - Helix
      4.2.4 Collagen Helix
4.3 - Sheets: A Common Secondary Structural Element
4.4 Turns and Loops
4.5 Supersecondary and Tertiary Structure
      4.5.1 Complex 3D Networks
      4.5.2 Classes in Protein Architecture
      4.5.3 Classes are Further Divided into Folds
4.6 - Class Folds
      4.6.1 Bundles
      4.6.2 Folded Leafs
      4.6.3 Hairpin Arrays
4.7 - Class Folds
      4.7.1 Anti - Parallel Domains
      4.7.2 Parallel and Antiparallel Combinations
4.8 / and + - Class Folds
      4.8.1 / Barrels
      4.8.2 Open Twisted / Folds
      4.8.3 Leucine-Rich / Folds
      4.8.4 + Folds
4.9 Number of Folds
      4.9.1 Finite Number?
      4.9.2 Concerted Target Selection: Structural Genomics
4.10 Quaternary Structure
      4.10.1 Viruses
      4.10.2 From Ribosomes to Dynamic Networks
4.11 Structure Classification
5 Nucleic Acids Structure Minitutorial
5.1 DNA, Life's Blueprint
      5.1.1 The Kindled Field of Molecular Biology
      5.1.2 DNA Processes
      5.1.3 Challenges in Nucleic Acid Structure
      5.1.4 Chapter Overview
5.2 Basic Building Blocks
      5.2.1 Nitrogenous Bases
      5.2.2 Hydrogen Bonds
      5.2.3 Nucleotides
      5.2.4 Polynucleotides
      5.2.5 Stabilizing Polynucleotide Interactions
      5.2.6 Chain Notation
      5.2.7 Atomic Labeling
      5.2.8 Torsion Angle Labeling
5.3 Conformational Flexibility
      5.3.1 The Furanose Ring
      5.3.2 Backbone Torsional Flexibility
      5.3.3 The Glycosyl Rotation
      5.3.4 Sugar/Glycosyl Combinations
      5.3.5 Basic Helical Descriptors
      5.3.6 Base - Pair Parameters
5.4 Canonical DNA Forms
      5.4.1 B-DNA
      5.4.2 A-DNA
      5.4.3 Z-DNA
      5.4.4 Comparative Features
6 Topics in Nucleic Acids Structure
6.1 Introduction
6.2 DNA Sequence Effects
      6.2.1 Local Deformations
      6.2.2 Orientation Preferences in Dinucleotide Steps
      6.2.3 Intrinsic DNA Bending in A-Tracts
      6.2.4 Sequence Deformability Analysis Continues
6.3 DNA Hydration and Ion Interactions
      6.3.1 Resolution Difficulties
      6.3.2 Basic Patterns
6.4 DNA/Protein Interactions
      Supplement to section 6.4
6.5 Variations on a Theme
      6.5.1 Hydrogen Bonding Patterns in Polynucleotides
      6.5.2 Hybrid Helical/Nonhelical Forms
      6.5.3 Overstretched and Understretched DNA
6.6 RNA Structure
      6.6.1 RNA Chains Fold Upon Themselves
      6.6.2 RNA's Diversity
      6.6.3 RNA at Atomic Resolution
      6.6.4 Emerging Themes in RNA Structure and Folding
6.7 Cellular Organization of DNA
      6.7.1 Compaction of Genomic DNA
      6.7.2 Coiling of the DNA Helix Itself
      6.7.3 Chromosomal Packaging of Coiled DNA
6.8 Mathematical Characterization of DNA Supercoiling
      6.8.1 DNA Topology and Geometry
6.9 Computational Treatments of DNA Supercoiling
      6.9.1 DNA as a Flexible Polymer
      6.9.2 Elasticity Theory Framework
      6.9.3 Simulations of DNA Supercoiling
7 Theoretical and Computational Approaches to Biomolecular Structure
7.1 Merging of Theory and Experiment
      7.1.1 Exciting Times for Computationalists!
      7.1.2 The Future of Biocomputations
      7.1.3 Chapter Overview
7.2 QM Foundations
      7.2.1 The Schrodinger Wave Equation
      7.2.2 The Born-Oppenheimer Approximation
      7.2.3 Ab Initio
      7.2.4 Semi-Empirical QM
      7.2.5 Recent Advances in Quantum Mechanics
      7.2.6 From Quantum to Molecular Mechanics
7.3 Molecular Mechanics Principles
      7.3.1 The Thermodynamic Hypothesis
      7.3.2 Additivity
      7.3.3 Transferability
7.4 Molecular Mechanics Formulation
      7.4.1 Configuration Space
      7.4.2 Functional Form
      7.4.3 Some Current Limitations
8 Force Fields
8.1 Formulation of the Model and Energy
8.2 Normal Modes
      8.2.1 Characteristic Motions
      8.2.2 Spectra of Biomolecules
      8.2.3 Spectra As Force Constant Sources
      8.2.4 In-Plane and Out-of-Plane Bending
8.3 Bond Length Potentials
      8.3.1 Harmonic Term
      8.3.2 Morse Term
      8.3.3 Cubic and Quartic Term
8.4 Bond Angle Potentials
      8.4.1 Harmonic and Trigonometric Terms
      8.4.2 Cross Bond Stretch / Angle Bend Terms
8.5 Torsional Potentials
      8.5.1 Origin of Rotational Barriers
      8.5.2 Fourier Terms
      8.5.3 Torsional Parameter Assignment
      8.5.4 Improper Torsion
      8.5.5 Cross Dihedral/Bond Angle and Improper/Improper Dihedral Terms
8.6 van der Waals Potential
      8.6.1 Rapidly Decaying Potential
      8.6.2 Parameter Fitting From Experiment
      8.6.3 Two Parameter Calculation Protocols
8.7 Coulombic Potential
      8.7.1 Coulomb's Law: Slowly Decaying Potential
      8.7.2 Dielectric Function
      8.7.3 Partial Charges
8.8 Parameterization
      8.8.1 A Package Deal
      8.8.2 Force Field Performance
9 Nonbonded Computations
9.1 Computational Bottleneck
9.2 Reducing Computational Cost
      9.2.1 Simple Cutoff Schemes
      9.2.2 Ewald and Multipole Schemes
9.3 Spherical Cutoff Techniques
      9.3.1 Technique Categories
      9.3.2 Guidelines for Cutoff Functions
      9.3.3 General Cutoff Formulations
      9.3.4 Potential Switch
      9.3.5 Force Switch
      9.3.6 Shift Functions
9.4 Ewald Method
      9.4.1 Periodic Boundary Conditions
      9.4.2 Ewald Sum and Crystallography
      9.4.3 Morphing a Conditionally Convergent Sum
      9.4.4 Finite-Dielectric Correction
      9.4.5 Ewald Sum Complexity
      9.4.6 Resulting Ewald Summation
      9.4.7 Practical Implementation
9.5 Multipole Method
      9.5.1 Basic Hierarchical Strategy
      9.5.2 Historical Perspective
      9.5.3 Expansion in Spherical Coordinates
      9.5.4 Biomolecular Implementations
      9.5.5 Other Variants
9.6 Continuum Solvation
      9.6.1 Need for Simplification!
      9.6.2 Potential of Mean Force
      9.6.3 Stochastic Dynamics
      9.6.4 Continuum Electrostatics
10 Multivariate Minimization in Computational Chemistry
10.1 Optimization Applications
      10.1.1 Algorithmic Understanding Needed
      10.1.2 Chapter Overview
10.2 Fundamentals
      10.2.1 Problem Formulation
      10.2.2 Independent Variables
      10.2.3 Function Characteristics
      10.2.4 Local and Global Minima
      10.2.5 Derivatives
      10.2.6 Hessian Matrix
10.3 Basic Algorithms
      10.3.1 Greedy Descent
      10.3.2 Line Searches
      10.3.3 Trust Region Methods
      10.3.4 Convergence Criteria
10.4 Newton's Method
      10.4.1 Newton in One Dimension
      10.4.2 Newton's Method for Minimization
      10.4.3 Multivariate Newton
10.5 Large-Scale methods
      10.5.1 Quasi-Newton (QN)
      10.5.2 Conjugate Gradient (CG)
      10.5.3 Truncated-Newton (TN)
      10.5.4 Simple Example
10.6 Software
      10.6.1 Popular Newton and CG
      10.6.2 CHARMM's ABNR
      10.6.3 CHARMM's TN
      10.6.4 Comparative Performance on Molecular Systems
10.7 Recommendations
10.8 Future Outlook
11 Monte Carlo Techniques
11.1 Monte Carlo Popularity
      11.1.1 A Winning Combination
      11.1.2 From Needles to Bombs
      11.1.3 Chapter Overview
      11.1.4 Importance of Error Bars
11.2 Random Number Generators
      11.2.1 What is Random?
      11.2.2 Properties of Generators?
      11.2.3 Linear Congruential Generators
      11.2.4 Other Generators
      11.2.5 Artifacts
      11.2.6 Recommendations
11.3 Gaussian Random Variates
      11.3.1 Manipulation of Uniform Random Variables
      11.3.2 Normal Variates in Molecular Simulations
      11.3.3 Odeh/Evans
      11.3.4 Box/Muller/Marsaglia
11.4 Monte Carlo Means
      11.4.1 Expected Values
      11.4.2 Error Bars
      11.4.3 Batch Means
11.5 Monte Carlo Sampling
      11.5.1 Probability Density Function
      11.5.2 Equilibria or Dynamics
      11.5.3 Ensembles
      11.5.4 Importance Sampling
11.6 Hybrid MC
      11.6.1 MC and MD
      11.6.2 Basic Idea
      11.6.3 Variants and Other Hybrid Approaches
12 Molecular Dynamics: Basics
12.1 Introduction
      12.1.1 Why Molecular Dynamics?
      12.1.2 Background
      12.1.3 Outline of MD Chapters
12.2 Laplace's Vision
      12.2.1 The Dream
      12.2.2 Deterministic Mechanics
      12.2.3 Neglect of Electronic Motion
      12.2.4 Critical Frequencies
      12.2.5 Electronic/Nuclear Treatment
12.3 Basics
      12.3.1 Following Motion
      12.3.2 Trajectory Quality
      12.3.3 Initial System Setting
      12.3.4 Trajectory Sensitivity
      12.3.5 Simulation Protocol
      12.3.6 High-Speed Implementations
      12.3.7 Analysis and Visualization
      12.3.8 Reliable Numerical Integration
      12.3.9 Computational Complexity
12.4 Verlet Algorithm
      12.4.1 Position and Velocity Propagation
      12.4.2 Leapfrog, Velocity Verlet, and Position Verlet
12.5 Constrained Dynamics
12.6 Various MD Ensembles
      12.6.1 Ensemble Types
      12.6.2 Simple Algorithms
      12.6.3 Extended System Methods
13 Molecular Dynamics: Further Topics
13.1 Introduction
13.2 Symplectic Integrators
      13.2.1 Symplectic Transformation
      13.2.2 Harmonic Oscillator Example
      13.2.3 Linear Stability
      13.2.4 Timestep-Dependent Rotation in Phase Space
      13.2.5 Resonance Condition for Periodic Motion
      13.2.6 Resonance Artifacts
13.3 Multiple-Timestep (MTS) Methods
      13.3.1 Basic Idea
      13.3.2 Extrapolation
      13.3.3 Impulses
      13.3.4 Resonances in Impulse Splitting
      13.3.5 Resonance Artifacts in MTS
      13.3.6 Resonance Consequences
13.4 Langevin Dynamics
      13.4.1 Uses
      13.4.2 Heat Bath
      13.4.3 Effect of
      13.4.4 Generalized Verlet for Langevin Dynamics
      13.4.5 LN Method
13.5 Brownian Dynamics (BD)
      13.5.1 Brownian Motion
      13.5.2 Brownian Framework
      13.5.3 General Propagation Framework
      13.5.4 Hydrodynamics
      13.5.5 BD Propagation
13.6 Implicit Integration
      13.6.1 Implicit vs. Explicit Euler
      13.6.2 Intrinsic Damping
      13.6.3 Computational Time
      13.6.4 Resonance Artifacts
13.7 Future Outlook
      13.7.1 Integration Ingenuity
      13.7.2 Current Challenges
14 Similarity and Diversity in Chemical Design
14.1 Introduction to Drug Design
      14.1.1 Chemical Libraries
      14.1.2 Early Days
      14.1.3 Rational Drug Design
      14.1.4 Automated Technology
      14.1.5 Chapter Overview
14.2 Database Problems
      14.2.1 Database Analysis
      14.2.2 Similarity and Diversity Sampling
      14.2.3 Bioactivity
14.3 General Problem Definitions
      14.3.1 The Dataset
      14.3.2 The Compound Descriptors
      14.3.3 Biological Activity
      14.3.4 The Target Function
      14.3.5 Scaling Descriptors
      14.3.6 The Similarity and Diversity Problem
14.4 Data Compression and Cluster Analysis
      14.4.1 PCA compression
      14.4.2 SVD compression
      14.4.3 PCA and SVD
      14.4.4 Projection Application
      14.4.5 Example
14.5 Future Perspectives
Appendix A Syllabus  (PDF)
Appendix B Article Reading List
Appendix C General Reference List
Appendix D Homeworks
Bibliography
References




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