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柚木克之 (YUGI, Katsuyuki) Kuroda Lab., The University of Tokyo Underlying mechanisms of biochemical oscillations 2012724日火曜日

Selkov Oscillation Lecturer

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  • (YUGI, Katsuyuki)

    Kuroda Lab., The University of Tokyo

    Underlying mechanisms of biochemical oscillations

    2012724

  • Electrocardiograph

    2012724

  • 2012724

  • k1.2x102sec1

    BorisukandTyson(1998)

    2012724

  • Hes1(Notch signalling system)

    mRNA2

    Hirata et al. (2002) Science

    MAPK2

    , 2006

    Nakayama et al. (2008) Curr. Biol.

    In depth

    2012724

  • Relaxation oscillator (e.g. Selkov model)

    Hopf

    Negative feedback oscillator (e.g. Repressilator)

    2012724

  • Selkov

    2012724

  • Strogatz(1994)pp.205

    Selkov

    {x = v2 v3y = v1 v2

    v2 = ay + x2yv1 = bv3 =x

    v1 v2 v3ADP(x)F6P(y)PFK

    2012724

  • Kennedy et al. (2007)

    2012724

  • Bertram et al. (2007) Corkey et al. (1988)

    insulin

    2012724

  • Luteinizing hormone

    Growth hormone ()Adrenocorticotropic hormone

    Insulin

    2012724

  • 15

    2 2 211 min 11 min

    insulin

    insulin

    insulin

    Continuous insulin gluc

    ose

    prod

    uctio

    n

    mol

    /kg/

    min

    13min

    26min

    2012724

  • : a = 0.06, b = 0.6

    : ADP = 1.0, F6P = 1.0

    Strogatz(1994)pp.205

    1(MATLAB): Selkov model

    {x = v2 v3y = v1 v2

    v2 = ay + x2yv1 = bv3 = x

    v1 v2 v3ADP(x)F6P(y)PFK

    2012724

  • function selkov( ) time = 0.001:1:100; s0 = [1.0 , 1.0]; % Initial values param = [0.06 , 0.6]; % Constants [t,time_course] = ode15s(@(t,s) ODE(t,s,param),time,s0); figure; plot(t,time_course); end

    function dsdt = ODE(t,s,param) ADP = s(1); F6P = s(2); a = param(1); b = param(2); v1 = v2 = v3 = dsdt(1,:) = dsdt(2,:) =end

    2012724

  • : ADP

    :F6P

    2012724

  • function selkov( ) time = 0.001:1:100; s0 = [1.0 , 1.0]; % Initial values param = [0.06 , 0.6]; % Constants [t,time_course] = ode15s(@(t,s) ODE(t,s,param),time,s0); figure; plot(t,time_course); end

    function dsdt = ODE(t,s,param) ADP = s(1); F6P = s(2); a = param(1); b = param(2); v1 = b; v2 = a * F6P + ADP^2 * F6P; v3 = ADP; dsdt(1,:) = v2 v3; dsdt(2,:) = v1 v2;end

    2012724

  • 1David Baltimore

    2012724

  • RockefellerCaltech

    Baltimore

    2012724

  • Baltimore

    2012724

  • Hoffmann et al. (2002) Science

    2012724

  • NF-B

    IBNF-B IKKIB

    IB NF-B

    NF-BIB

    NF-B

    NF-B

    2012724

  • ()

    ()

    EMSA(Electrophoretic Mobility Shift Assay)

    2012724

  • (feedback)

    2012724

  • 1

    2012724

  • Phase plane ()

    2

    x-y

    Nullcline ()

    = 0

    [ADP]

    [F6P]

    x = 0

    y = 0

    2012724

  • Selkov (MATLAB)

    ([ADP],[F6P])2

    MATLAB

    2:

    2012724

  • function selkov_phaseplane( ) time = 0.001:1:50; plot_phase_plane(time_course,param(1),param(2));end function plot_phase_plane(time_course,a,b) figure; hold on; % plot( , ); % ADP = 0:0.1:3; F6P = ADP ./ ( a + ADP.^2 ); % dADP / dt == 0 plot(ADP,F6P,r); % rredr ADP = 0:0.1:3; % d F6P / dt == 0 plot( , , ); hold off;end

    function dsdt = ODE(t,s,param) ()

    2012724

  • :

    2012724

  • function selkov_phaseplane( ) time = 0.001:1:50; plot_phase_plane(time_course,param(1),param(2));end function plot_phase_plane(time_course,a,b) figure; hold on; % plot(time_course(:,1),time_course(:,2)); ADP = 0:0.1:3; F6P = ADP ./ ( a + ADP.^2 ); % dADP / dt == 0 plot(ADP,F6P,r); % rredr ADP = 0:0.1:3; F6P = b ./ ( a + ADP.^2 ); % d F6P / dt == 0 plot(ADP,F6P,r); hold off;end

    2012724

  • [ADP]

    [F6P]

    (1,2)

    5

    2

    ( x , y ) ( , )

    {x = f(x, y)y = g(x, y)

    {x = x + 2y + x2yy = 8 2y x2y

    2012724

  • x

    ( , ) = ( 0 , p )

    : =0

    : =0

    [ADP]

    [F6P]

    = 0

    = 0

    2012724

  • ()

    x()

    y

    3a: Selkov

    2012724

  • [ADP]

    [F6P]

    = 0

    = 0

    2012724

  • Selkovfigure(MATLAB)

    quiver

    meshgrid

    3b: Selkov

    2012724

  • [X,Y] = meshgrid(0.01:0.2:2, 0.01:0.2:2);

    DX = -X + a * Y + X.^2 .* Y;

    DY = b - a * Y - X.^2 .* Y;

    (X,Y)(DX,DY)

    quiver(X,Y,DX,DY);

    : MATLAB

    2012724

  • function selkov_vector_field () ()function ODE(t,s,param)()function plot_phase_plane(time_course, a, b)()

    function plot_vector_field(a,b) figure(1); [X,Y] = meshgrid( ); DX = DY = quiver( ); %(X,Y)(DX,DY)end

    2012724

  • 2012724

  • function selkov_vector_field () ()function ODE(t,s,param)()function plot_phase_plane(time_course, a, b)()

    function plot_vector_field(a,b) figure(1); [X,Y] = meshgrid(0.01:0.2:3, 0.01:0.2:10); DX = -X + a * Y + X.^2 .* Y; DY = b - a * Y - X.^2 .* Y; quiver(X,Y,DX,DY); %(X,Y)(DX,DY)end

    2012724

  • 2Arnold Levine

    2012724

  • Rockefeller

    p53Levine

    2012724

  • Lev Bar-Or et al. (2000) PNAS

    2012724

  • p53

    ()

    p53Mdm2

    2012724

  • 2012724

  • 2

    2012724

  • [ADP]

    [F6P]

    = 0

    = 0

    2012724

  • 2

    [ADP]

    [F6P]

    [ADP]

    [F6P]

    2012724

  • d

    dtx1 = F1(x1, , xn)

    ...d

    dtxn = Fn(x1, , xn)

    d

    dt

    x1...xn

    =

    F1x1

    F1xn...

    . . ....

    Fnx1

    Fnxn

    x1...

    xn

    F1x1

    F1x1

    F1xn

    dx1dt

    = F1(x1, , xn)

    dx1dt

    = F1(x1, , xn)

    2012724

  • Selkov (MATLAB)

    (MATLAB)

    (MATLAB)

    (MATLAB)

    4: Selkov

    (xx

    xy

    yx

    yy

    )

    xx =

    x(x+ ay + x2y)

    yx =

    y(x+ ay + x2y)

    2012724

  • f

    diff(f, x);

    f

    f = -x + a * y + x^2 * y;

    J =[ diff(f,x) , diff(f,y) ; diff(g,x) , diff(g,y) ];

    MATLAB

    2012724

  • Symbolic Math ToolBox

    syms x y a b; %x, y, a, b

    x, y

    S = solve( -x + a * y + x^2 * y=0,'b - a * y - x^2 *y=0', 'x', 'y');

    Sx,y

    xS.x

    2012724

  • J = subs(J, [a,b] ,[0.06,0.6])

    % Ja,b0.06,0.6

    A

    eig(A)

    2012724

  • function selkov_jacobian( )syms x y a b;S = solve(' ',' ',' ',' '); % x, yf = -x + a * y + x^2 * y;g = J = [ ; %fx,y ]; %gx,y

    fix = subs([S.x,S.y],[ , ],[ , ]) %a,b0.06,0.6J = subs(J, [ , ,,a,b] ,[ , ,0.06,0.6]) %Ja,b0.06,0.6 %end

    2012724

  • >> selkov_jacobian

    fix =

    0.6000 1.4286

    J =

    0.7143 0.4200-1.7143 -0.4200

    ans =

    0.1471 + 0.6311i0.1471 - 0.6311i>>

    2012724

  • yx =

    y(x+ ay + x2y) = a+ x2

    xx =

    x(x+ ay + x2y) = 1 + 2xy

    xy =

    x(b ay x2y) = 2xy

    yy =

    y(b ay x2y) = a x2

    (1 + 2b2a+b2 a+ b2

    2b2a+b2 a b2)

    ( 1 + 2xy a+ x22xy a x2

    )(b ,

    b

    a+ b2

    )

    2012724

  • function selkov_jacobian( )syms x y a b;S = solve('-x + a * y + x^2 * y=0','b - a * y - x^2 * y=0','x','y'); % x, yf = -x + a * y + x^2 * y;g = b - a * y - x^2 * y; J = [ diff(f,x) , diff(f,y); %fx,y diff(g,x) , diff(g,y) ]; %gx,y

    fix = subs([S.x,S.y],[a,b],[0.06,0.6]) %a,b0.06,0.6J = subs(J, [x,y,a,b] ,[fix(1),fix(2),0.06,0.6]) %Ja,b0.06,0.6eig(J) %end

    2012724

  • (Node)

    : (attractor)

    : (repellor)

    (Saddle)

    :

    : StableNode Saddle

    d

    dtx = Jx

    x(t) = exp(Jt)x0= c1 exp(1t)v1 + cn exp(nt)vn

    x

    y

    x

    y

    2012724

  • (Spiral)

    (Focus)

    (Center)

    StableSpiral

    Center

    UnstableSpiral

    (Eulers formula)

    x

    y

    x

    y

    x

    y

    2012724

  • Selkov()a=0.06, b=0.6

    1:

    Ax=x|A-I|=02x2 2-tr(A) +det(A)=0

    2: = tr(A) = 1 + 2 = det(A) =12

    < 0 > 0

    24 > 0

    5: Selkov

    2012724

  • > 0 2 a,b

    a=0.06, b=0.6

    24 < 0 > 0

    = det(J) = a+ b2 > 0

    J =

    (1 + 2b2a+b2 a+ b2

    2b2a+b2 a b2)

    = tr(J) = (a+ b2) a b2

    a+ b2

    2012724

  • 3

    2012724

  • 2

    8130

    260

    http://bsw3.naist.jp/courses/courses106.html

    http://www.nig.ac.jp/hot/2006/saga0606-j.html

    2012724

  • NIH

    2012724

  • Q. 2hr?

    A. Hes1, Smad, Stat

    2012724

  • 2012724

  • 2012724

  • ()

    2012724

  • 3

    2012724

  • (limit cycle)

    (trajectory)

    Center ()

    Center

    Poincar-Bendixson

    Center

    Limitcycle

    2012724

  • Re

  • Stable Spiral Unstable Spiral

    Unstable Spiral

    Hopf

    Hopf

    2012724

  • Selkov 2Hopf ()

    1: a=0.14, b=0.6

    2: a=0.06, b=0.6

    MATLAB

    6: SelkovHopf

    2012724

  • a=0.06, b=0.6 >0

    a=0.14, b=0.6 0

    1,2 -4 < 0

    = (a+ b2) a b2

    a+ b2

    4 = 5(a+ b2) a b2

    a+ b2

    2012724

  • a=0.14, b=0.6 a=0.06, b=0.6

    2012724

  • Relaxation oscillatorand

    Negative feedback oscillator

    2012724

  • Relaxation oscillator ()

    2

    Negative feedback oscillator ()

    3

    ? Bendixson

    2

    2012724

  • D

    D

    Bendixson

    f1x1

    +f2x2

    ([F6P])[F6P]

    +([ADP])[ADP]

    2012724

  • 1(positive)

    1negative feedback loop

    ()

    Relaxation oscillator

    J =(+ ??

    )

    2012724

  • 2negative feedback oscillators (Bendixson)

    ()

    3

    Bendixson

    Negative feedback oscillator

    J =( ?

    ? )

    2012724

  • 7: SelkovBendixson

    Selkov

    > 0

    2012724

  • function selkov_bendixson( ) syms x y a b; f = % ODE g = % ODE J = % f, gJ J = subs(J, [a,b] ,[0.06 , 0.6]); % a,b B = %

    figure(1) hold on; for i=0:0.5:3 % x for j=0:1:10 % y B_value = subs( ); % Bx,yi,j if( B_value > 0 ) plot(i,j,'ko','MarkerFaceColor','w'); else plot(i,j,'ko','MarkerFaceColor','k'); end end endend

    2012724

  • 2012724

  • function selkov_bendixson( ) syms x y a b; f = -x + a * y + x^2 * y; g = b - a * y - x^2 * y; J = [ diff(f,x) , diff(f,y); diff(g,x) , diff(g,y)]; J = subs(J, [a,b] ,[0.06 , 0.6]); % a,b B = J(1,1)+J(2,2); %

    figure(1) hold on; for i=0:0.5:3 % x for j=0:1:10 % y B_value = subs( B, [x,y], [i,j] ); % Bx,yi,j if( B_value > 0 ) plot(i,j,'ko','MarkerFaceColor','w'); else plot(i,j,'ko','MarkerFaceColor','k'); end end endend

    2012724

  • (bifurcation diagram)(phase diagram)

    1 ()

    2(a, b)

    LacY

    -GFP b

    a2012724

  • ab

    8: Selkov ()

    2012724

  • plot(x,y,'ko','MarkerFaceColor','k'); plot(x,y,'ko','MarkerFaceColor','w'); plot(x,y,'ko','MarkerEdgeColor','r','MarkerFaceColor','r'); plot(x,y,'ko','MarkerEdgeColor','r','MarkerFaceColor','w');

    1 isreal(n)

    real(c)

    1

    2012724

  • for a , b

    if

    if ( isreal(v(1)) )

    OK ()

    if

    if( real(v(1)) < 0 )

    2

    2012724

  • function selkov_phase_diagram()figure;hold on;

    for a=0.01:0.01:0.15for b=0.1:0.1:1.0endendend

    function v=jacobian( p , q ) syms x y a b;S = solve(' -x + a * y + x^2 * y=0','b - a * y - x^2 * y=0','x','y'); f = -x + a * y + x^2 * y;g = b - a * y - x^2 * y;J = [ diff(f,x) , diff(f,y);diff(g,x) , diff(g,y)];

    fix = subs([S.x,S.y],[a,b],[p,q]);J = subs(J, [x,y,a,b] ,[fix(1),fix(2),p,q]);v = eig(J);end

    (1/2)

    2012724

  • function phase_diagram( a , b )v=jacobian(a,b);

    if ( isreal(v(1)) ) % v(1)v(2)v(1)if( v(1) < 0 && v(2) < 0 )plot();elseplot();endelseif( < 0 ) % v(1) < 0plot( );elseplot( );endendend

    (2/2)

    2012724

  • function selkov_phase_diagram()figure;hold on;

    for a=0.01:0.01:0.15for b=0.1:0.1:1.0phase_diagram(a,b);endendend

    function v=jacobian( p , q ) syms x y a b;S = solve(' -x + a * y + x^2 * y=0','b - a * y - x^2 * y=0','x','y'); f = -x + a * y + x^2 * y;g = b - a * y - x^2 * y;J = [ diff(f,x) , diff(f,y);diff(g,x) , diff(g,y)];

    fix = subs([S.x,S.y],[a,b],[p,q]);J = subs(J, [x,y,a,b] ,[fix(1),fix(2),p,q]);v = eig(J);end

    (1/2)

    2012724

  • function phase_diagram( a , b )v=jacobian(a,b);

    if ( isreal(v(1)) ) % v(1)v(2)v(1)if( v(1) < 0 && v(2) < 0 )plot(a,b,'ko','MarkerFaceColor','k'); else plot(a,b,'ko','MarkerFaceColor','w');endelseif( real(v(1)) < 0 ) % v(1) < 0plot(a,b,'ko','MarkerEdgeColor','r','MarkerFaceColor','r'); else plot(a,b,'ko','MarkerEdgeColor','r','MarkerFaceColor','w');endendend

    (2/2)

    2012724

  • ab

    : a, b

    Hopf

    2012724

  • Supercritical Hopf

    Selkov

    2012724

  • !

    Poincar-Bendixson

    Hopf

    2012724

  • Negative feedback oscillator

    2012724

  • Elowitz and Leibler (2000) Nature

    Repressilator

    2012724

  • (NOT)

    1 / ( 2n )

    Repressilator

    3

    hUp://133.6.66.95/mizutanilab3/ROC_ROCirc.html

    2012724

  • : Ring Oscillator

    2012724

  • 3()

    Repressilator

    {d[mRNA]

    dt = 0 +

    1+[Repressor]n [mRNA]d[Protein]

    dt = ([mRNA] [Protein])

    2012724

  • A n=2.1, 0=0

    B n=2, 0=0

    C n=2, 0/=103

    X

    Phase diagram

    2012724

  • inset

    X

    2012724

  • 40

    0.2-0.5 h-1

    2012724

  • (lacI, cI, tetR, LacI, CI, TetR) = (0.2, 0.3, 0.1, 0.1, 0.5, 0.4)

    =20, 0=0, =0.2, n=2

    9:

    {d[mRNA]

    dt = 0 +

    1+[Repressor]n [mRNA]d[Protein]

    dt = ([mRNA] [Protein])

    2012724

  • function repressilator( input_args ) time = 0.001:1:200; s0 = [0.2, 0.3, 0.1, 0.1, 0.5, 0.4]; % Initial values param = [20, 0, 0.2, 2]; % Constants [t,time_course] = ode15s(@(t,s) ODE(t,s,param),time,s0); plot_time_course(t,time_course); plot_phase_plane(time_course);end

    MATLAB(1/2)

    2012724

  • function dsdt = ODE(t,s,param) lacI = s(1); cI = s(2); tetR = s(3); LacI = s(4); CI = s(5); TetR = s(6); alpha = param(1); alpha_zero = param(2); beta = param(3); n = param(4); dsdt(1,:) = dsdt(2,:) = dsdt(3,:) = dsdt(4,:) = dsdt(5,:) = dsdt(6,:) = end

    MATLAB(2/2):

    2012724

  • 2012724

  • function dsdt = ODE(t,s,param) lacI = s(1); cI = s(2); tetR = s(3); LacI = s(4); CI = s(5); TetR = s(6); alpha = param(1); alpha_zero = param(2); beta = param(3); n = param(4); dsdt(1,:) = alpha_zero + alpha / ( 1 + CI^n ) - lacI; dsdt(2,:) = alpha_zero + alpha / ( 1 + TetR^n ) - cI; dsdt(3,:) = alpha_zero + alpha / ( 1 + LacI^n ) - tetR; dsdt(4,:) = - beta * ( LacI - lacI ); dsdt(5,:) = - beta * ( CI - cI ); dsdt(6,:) = - beta * ( TetR - tetR );end

    2012724

  • Plan A:

    2

    Plan B:

    Repressilator6Plan B

    Hopf

    2012724

  • 6

    Hopf

    m1p3

    =npn13(1 + p23)2

    = X

    p3 =

    1 + pn3+ 0

    ( + 1)2(2X + 4) 3X2 < 0

    J =

    1 0 0 0 0 X0 1 0 X 0 00 0 1 0 X 0 0 0 0 00 0 0 00 0 0 0

    p3

    2012724

  • 10: Hopf

    ( + 1)2(2X + 4) 3X2 < 0

    p3 =

    1 + pn3+ 0

    () =10, 0=0, n=2 p3 = 2

    p3

    =10, 0=0, n=2

    X =npn13(1 + p23)2

    2012724

  • =0.13 =0.14 (+1)2(2X+4)-3X2 = 0.0231 > 0 (+1)2(2X+4)-3X2 = -0.0355 < 0

    2012724

  • Hill

    (0)m

    2012724

  • Toggle switchPitchfork

    2012724

  • Toggle switchPitchfork

    : xy

    Gardner et al. (2000)

    x =a

    1 + y2 x

    y =a

    1 + x2 y

    LacI (x) CI (y)x y

    2012724

  • Pitchfork

    a=2 a>2

    a

    xx

    yy

    pitchfork

    Stable

    Stable

    Unstable

    y

    = 0

    = 0

    2012724

  • :

    1. Toggle switch

    a 1 3

    2. 11

    Stable Node 3 Stable Node 2 Unstable

    Node 1

    2012724

  • :

    3. y x

    x x5 - ax4 + 2x3 - 2ax2 + (1 + a2)x -

    a = 0

    4. 3 x x5 - ax4 + 2x3 - 2ax2

    + (1 + a2) x - a = 0 (x3 + x - a)(x2 - ax + 1) = 0

    2012724

  • : (1/2)

    5. x3 + ax + b = 0 3

    D = - 4a3 - 27b2 D > 0

    3 D = 0D < 0 1

    2

    x3 + x - a x3 + x - a = 0 1

    a

    2012724

  • : (2/2)

    6. x2 - ax + 1

    x2 - ax + 1 = 0 a > 2 2a = 2

    1a < 2

    7. 56 x (x3 + x -

    a)(x2 - ax + 1) = 0 (x3 + x - a)1

    (x2 - ax + 1) a = 202

    Toggle switch 0 < a < 2 a = 2 a > 2

    a = 2

    2012724

  • : (1/2)

    8. Toggle-switch

    9. a > 2 x2 - ax + 1 = 0

    (i)

    (ii) 2

    (: )

    (1 2ay(1+y2)2

    2ax(1+x2)2 1

    )

    (aa2 4

    2,aa2 4

    2

    )

    2012724

  • : (2/2)

    10. x3 + x - a = 0 x

    x

    (i) a = 2 x = 1 x a 0 < a < 2 0 < x < 1 a > 2 x > 1

    (ii) 0 < x < 1 0 < a < 2 > 0 x > 1 a > 2 < 0

    x =3

    a2+

    (a2

    )2+(13

    )3 1

    3 3

    a2 +

    (a2

    )2 + ( 13)3

    2012724

  • : Pitchfork

    11. 7.10.

    a

    x

    0

  • 1(1/2)

    y =a

    1 + x2 = 0

    13x

    y ---y - 0 +

    y

    y =0 (1 + x2) a 2x

    (1 + x2)2

    = 2ax(1 + x2)2

    y =2a(1 + x2)2 (2ax) 2(1 + x2) 2x

    (1 + x2)4

    =2a(1 + x2){(1 + x2) 2x 2x}

    (1 + x2)4

    =2a(1 + x2)(13x)(1 +3x)

    (1 + x2)4

    x

    ya

    13

    = 0

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  • 1(2/2)

    = 0 y = x 2

    x

    y

    a

    = 0

    = 0

    a

    y = x

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  • 2

    x

    y = 0

    ax

    y

    = 0

    a

    x

    ya

    = 0

    = 0

    a2012724

  • 3

    y =a

    1 + x2x =

    a

    1 + y2

    x =a

    1 +(

    a1+x2

    )2=

    a(1 + x2)2

    (1 + x2)2 + a2

    (1 + x2)2x+ a2x = a(1 + x2)2

    x+ 2x3 + x5 + a2x = a+ 2ax2 + ax4

    x5 ax4 + 2x3 2ax2 + (1 + a2)x a = 0

    2012724

  • 4

    (x3 + x a)(x2 ax+ 1) = 0x5 ax4 + x3 + x3 ax2 + x ax2 + a2x a = 0

    x5 ax4 + 2x3 2ax2 + (1 + a2)x a = 0

    2012724

  • 5-7

    5. x3 + x - a = 0 D = - 4 - 27a2 < 0

    12

    6. x2 - ax + 1 = 0 D = a2 - 4 a > 2

    D > 0 2a = 2 D = 0

    1 a < 2 D < 0

    7.

    0

  • 8 x =a

    1 + y2 x

    y =a

    1 + x2 y

    xx = 1

    yx = 2ay

    (1 + y2)2

    yy = 1

    yx = 2ax

    (1 + x2)2(1 2ay(1+y2)2

    2ax(1+x2)2 1

    )

    2012724

  • 9-(ii) =1 4a

    2xy

    (1 + x2)2(1 + y2)2

    = 1 4a2xy

    (1 + x2 + y2 + x2y2)2

    xy =(aa2 4)(aa2 4)

    4= 1

    =1 4a2

    (2 + x2 + y2)2

    = 1 4a2

    (2 + 4a284 )2

    = 1 4a2

    a4

    = 1 4a2

    > 0 ( a > 2)

    0, 2-4>02

    2012724

  • 10

    (i) 0 < a < 2 x x

    a = 0 x = 0 a = 2 x

    = 1 x a 0 < a < 2

    x 0 1

    0 < x < 1

    (ii) y=x

    =1 4a2xy

    (1 + x2)2(1 + y2)2

    = 1 4a2x2

    (1 + x2)4

    ddx

    = 1 8a2x(1 + x2)3(x 1)2

    (1 + x2)4 x

    a = 0, x = 0 = 1a = 2, x = 1 = 0

    0 < a < 2 1 > > 0a > 2 < 0

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  • 11

    x

    a2

    1

    NodeSaddle

    x3 + x - a = 0

    x2 - ax + 1 = 0

    x2 - ax + 1 = 0

    2012724

  • ?

    (Saddle-

    Node, Pitchfork)

    (Hopf)

    2012724

  • Further readings

    Strogatz, S.H, Nonlinear dynamics and chaos, Perseus Books Publishing, 1994. (ISBN 0-7382-0453-6)

    Borisuk and Tyson (1998)

    Fall, C.P., Marland, E.S., Wagner, J.M. and Tyson, J.J. Computational cell biology, Springer, 2002. (ISBN 0-387-95369-8)

    Bendixson

    Borisuk, M.T. and Tyson, J.J., Bifurcation analysis of a model of mitotic control in frog eggs, J. Theor. Biol. 195:69-85, 1998.

    2012724