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Contents

Contents i

Acknowledgments iv

Abstract – R´ esum´ e vi

1 Introduction 1

1.1 Context . . . . 1

1.2 Modelling strategy . . . . 3

1.2.1 Generalities . . . . 3

1.2.2 The mesoscopic approach . . . . 4

1.3 Objectives . . . . 9

I Effects of compartmentalisation on nonlinear chem- ical reactions 13 2 Nonlinear behaviour and fluctuation-induced dynamics in the photosensitive BZ reaction 14 2.1 Reaction mechanism and models . . . . 15

2.1.1 The Field-K¨ or¨ os-Noyes model . . . . 15

2.1.2 Modelling of the compartmentalised BZ reaction . . . . 17

2.2 Deterministic analysis . . . . 19

2.2.1 The non-photosensitive BZ reaction . . . . 20

2.2.2 The photosensitive BZ reaction . . . . 24

2.3 Stochastic simulations . . . . 27

2.3.1 The non-photosensitive case . . . . 29

2.3.2 The photosensitive case . . . . 34

2.4 Discussion . . . . 37

i

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Contents 3 Emergence of chaos in a spatially confined reactive system 39

3.1 Introduction . . . . 39

3.2 The amended Willamowski-R¨ ossler model . . . . 41

3.3 Deterministic behaviour . . . . 44

3.4 Stochastic dynamics . . . . 48

3.4.1 Fluctuations in a homogeneous system . . . . 48

3.4.2 Inhomogeneous fluctuations . . . . 51

3.5 Discussion . . . . 58

II Calcium release from IP

3

Rs clusters : from local to global signals 60 4 Introduction to calcium signalling 61 4.1 Compartmentalisation of the cell and calcium fluxes . . . . 62

4.2 Interactions between IP

3

Rs . . . . 65

4.2.1 Blips and puffs . . . . 66

4.2.2 Spikes and waves . . . . 68

4.3 Statistical properties of puffs and spikes . . . . 70

4.4 Models . . . . 72

4.4.1 Puff models . . . . 72

4.4.2 Modelling of spikes and waves . . . . 73

4.4.3 An effective cluster model . . . . 77

5 Emergence of global signals from clusters dynamics: a deter- ministic approach 80 5.1 Spatially homogeneous model . . . . 81

5.1.1 Governing equations and properties of the model . . . 81

5.1.2 Bistable regime . . . . 83

5.1.3 Oscillatory regime . . . . 89

5.2 Reaction-diffusion model . . . . 97

5.2.1 Governing equations and properties of the model . . . 97

5.2.2 Nucleation phenomena in the bistable regime . . . . . 99

5.2.3 Spatiotemporal patterns in the oscillatory regime . . . 102

5.3 Discussion . . . 105

6 Fully stochastic modelling of global spikes 108 6.1 The fully stochastic model . . . 109

6.1.1 Problem formulation and numerical code . . . 109

6.1.2 Macroscopic limit . . . 113

6.1.3 Comparison with the model by Calabrese et al. . . . . 117

ii

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Contents

6.2 Stochastic bistable regime . . . 119

6.2.1 Influence of ρ

c

on the global Ca

2+

dynamics . . . 120

6.2.2 Influence of the local σ on Ca

2+

dynamics . . . 125

6.3 Coupling strength between the clusters . . . 128

6.3.1 Influence of D . . . 128

6.3.2 Influence of v

p

. . . 132

6.4 Stochastic oscillatory regime . . . 135

6.5 Conclusions . . . 137

General conclusions and outlook 139

A Fluorescence measurements of concentrations in cells: cali-

bration of fluorescence signals 145

Bibliography 147

iii

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