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Supplementary information, available at the NATURE Web page

By Andrea Elliott,2014-09-04 04:32
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Supplementary information, available at the NATURE Web pageSupp

    1 Supplementary Information

Table 1 Coordinations of chlorophylls and their interactions with local

    environments

    Hydrogen bond Chlorophylls in Central Hydrogen bond partner partner to Chlorophylls the pea LHC-II of Chlb C7-formyl ligands chlorophyll model (ref.1)1C13-keto group Chlb 601 Tyr 24 ; - - none Chla 602 a4 (Glu 65) Glu 65 - Tyr 44 N, Trp 46 N Chla 603 a5 (His 68) His 68 - Wat

    Chla 604 a6 (Gly 78) Wat 309 - Leu 113 N

    Chlb 605 Val 119 ; Gln 122 N, Ser 123 N - none

    Wat 308 Chlb 606 b6 (Gln 131) Wat 310 - (ligand of Chlb 607)

    Chlb 607 a7 (unidentified) Wat 308 Gln 131 NE2 -

    Chlb 608 b1 (unidentified) Wat 302 Leu 148 N Arg 70 NH1

    Chlb 609 b5 (Glu 139) Glu 139 Gln 131 NE2 His 68 ND1

    Chla 610 a1 (Glu 180) Glu 180 - Gly 158 N

    Phospho-diChla 611 b2 (unidentified) - - ester

    Chla 612 a2 (Asn 183) Asn 183 - -

    Chla 613 a3 (Gln 197) Gln 197 - -

    Chla 614 b3 (His 212) His 212 - -

    ; These residues contribute their backbone carbonyls to coordinate with the central

    magnesium of chlorophylls.

    2

     Characters in parentheses indicate the chlorophyll central ligands identified in previous model.

    Table 2 Interaction between chlorophylls with strong excitonic coupling

    -1Chlorophyll pairs Excitonic coupling V (cm) Cos R (Å) R (Å) center

    Within a monomer

    Chla 611-612 144.9 -0.79 9.76 3.77

    Chlb 606-Chla 604 123.4 0.80 8.05 4.42

    Chla 603-Chlb 609 106.7 -0.88 9.74 3.97

    Chlb 608-Chla 610 69.2 -0.54 11.57 5.00

    Chlb 607-606 63.6 0.88 9.46 3.67

    Chla 613-614 -62.5 0.21 9.30 3.96

    Chlb 601-Chla 602 54.1 -0.69 12.79 5.51

    Between adjacent monomers within a trimer

    Chlb 609-601 42.0 0.10 11.79 4.95

    Between two adjacent trimers within an icosahedron

    Chlb 605-Chla 614 62.0 -0.61 12.16 5.40

    The Chla 611-612 pair located at the periphery of trimeric LHC-II exhibits the strongest coupling strength. The absorption of Chla 612 was observed to be red-shifted to about 680nm

    2,33which was proposed to be the lowest Q energy level in the complex. Rogl and Kühlbrandt y

    deduced that this Chla might be the terminal fluorescence emitter functioning in energy transmission to neighboring LHCs or to the reaction center. Our results indicate that strong excitonic coupling may be the most likely cause of the red shift. The next two strongly coupled pairs are Chla 603-Chlb 609 and Chla 604-Chlb 606. Our structural model serves as the basis for explaining the strong excitonic Chla-Chla and Chla-Chlb couplings detected by

    4-6spectroscopic methods. We also suggest that Chlb 607-606 pair with intermediate coupling

    7,8strength may be related to the observed sub-picosecond Chlb-to-Chlb energy transfer.

    3

     Excitonic coupling strength V is calculated according to Amerongen, H. V. and Grondelle, R.

    9V..

     The angle between two transition dipoles.

     The distance between the molecular centers of two chlorophylls. The coordinates of

    molecular centers of chlorophylls are calculated by arithmetically averaging the coordinates of

    the four pyrrole nitrogen atoms.

     Closest distance between two chlorin conjugated -systems.

    Table 3 Interactions between carotenoids and chlorophylls

    (| |k| |kCar-Chl pairs R R Cos Cos car_qxcar_qycenter

    Lut 620-Chla 610 3.61 9.91 -0.44 0.71 1.25 1.07

    Lut 620-Chla 612 3.65 6.03 -0.95 -0.33 1.01 0.10

    Lut 620-Chla 613 3.88 17.06 0.28 -0.69 0.21 1.72

    Lut 621-Chla 602 3.41 10.10 -0.42 0.59 1.23 1.09

    Lut 621-Chla 603 3.70 6.17 -0.90 -0.45 0.88 0.49

    Lut 621-Chla 604 4.10 17.25 0.37 -0.68 0.22 1.71

    Neo-Chlb 606 3.90 11.25 0.83 -0.20 1.67 0.51

    Neo-Chlb 608 4.70 8.24 -0.82 0.57 1.04 0.07

    Xanc-Chlb 601 4.40 11.53 0.89 -0.12 0.97 0.57

    Xanc-Chla 613 6.71 10.13 0.11 -0.92 0.36 0.79

    *Xanc-Chlb 607 4.91 12.80 0.88 -0.38 1.01 0.20

    Orientation factor k is expressed as k=~,-3(~r)(~r), where andare the 121122121 2

    normalized transition dipole moment vectors and ris the normalizedvector between the 12

    centers of pigments 1 and 2.

     Closest distance between the two conjugated -systems of carotenoids and chlorophylls. Distance between molecular centers of carotenoid and chlorophyll.

null

    5

     9. Amerongen, H. V. & Grondelle, R. V. Understanding the energy transfer function of

    LHCII, the major light-harvesting complex of green plants. J. Phys. Chem. B 105,

    604-617 (2001).

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