Fucoxanthin chlorophyll-a/c(2) protein (FCP), the membrane-intrinsic light harvesting complex from the diatom Cyclotella meneghiniana, is characterized by Stark spectroscopy to obtain a quantitative measure of the excited-state dipolar properties of the constituent pigments. The electro-optical properties of the carotenoid fucoxanthin (Fx), the primary light harvester in FCP, were determined from the Stark spectrum measured in a MeTHF glass (77 K) and compared to the results from electronic-structure calculations. On photon absorption by Fx, a 17 D change in the static dipole moment (vertical bar Delta(mu) over bar vertical bar exp), and a somewhat larger (vertical bar Delta(mu) over bar vertical bar(exp)), and a somewhat larger vertical bar Delta(mu) over bar vertical bar(exp) at the red edge, are measured for the S-0 -> S-2 (1(vertical bar)A(g)(-)-like -> 1(vertical bar)B(u)(*+)-like) transition. The large change in dipole moment indicates that Fx undergoes photoinduced charge transfer (CT), and underscores the influence of the S-2 state on the polarity-dependent excited-state dynamics of Fx that has so far been attributed to, and discussed in terms of, the S-0 and the S-1/ICT states. MNDO-PSDCI and SACCI-CISD calculations indicate that the 1(1)B(u)(*+)-like state intrinsically possesses a dipole moment much smaller than the 2(1)A*(-)(g)-like state, suggesting that solvent fields promote the mixing of these two states and could account for the large dipole moments measured here for the S-0 -> S-2 transition. These CT properties of the 1(1)B*(+)(u)-like state of Fx are further enhanced in the protein and underpin its photosynthetic capabilities for light harvesting and energy transfer (ET). In FCP, the CT properties of the Fx's vary according to the energetic position: between 450 and 500 nm there appear to be two sets of Fx's that exhibit vertical bar Delta(mu) over bar vertical bar(exp) values on the order of 5 and 15 D, whereas the red-most Fx's, that are very efficient in ET to chlorophyll-a (Chl-a), exhibit strikingly large vertical bar Delta(mu) over bar vertical bar(exp) values on the order of 40 D. Such magnitudes of vertical bar Delta(mu) over bar vertical bar(exp) suggest a mechanism that enhances Coulombic coupling to promote ET from the S-2 state of Fx to Ch1-a. These three sets of Fx's, including a fourth red Fx, are identified by fitting the Stark spectrum of FCP with the Stark spectrum of Fx in MeTHF. In contrast to the Fx's in the protein, the electrostatic properties of the Chl's in FCP are comparatively much smaller. Notably, for the Q(y) band of Ch1-a, a vertical bar Delta(mu) over bar vertical bar(exp) of 0.92 D and a change in polarizability ((Delta alpha) over bar (exp)) of 20 angstrom(3), indicate that the Ch1-a's are monomeric in nature and decoupled from each other.