Photophysical Consequences of Coupling Bacteriochlorophyll a with Serine and its Resulting Solubility in Water¶

Abstract

We investigated the dependence on solvents of optical absorption and emission of the bacteriochlorophyll a-serine (BChl-ser), a water soluble bacteriochlorophyll (BChl) derivative. Comparison between the experimental data and those collected for BChl in nonaqueous solvents shows that only a minor interaction takes place between serine and the macrocycle's pi-electron system. Nevertheless, the coupling with serine results in a small enhancement of the nonradiative relaxation rate from the first excited singlet state S1. In buffered aqueous solution (pH = 7.4), the Stokes shift of the BChl-ser fluorescence and its nonradiative relaxation rate are enhanced compared with those in nonaqueous solutions (Scherz, A., S. Katz, Y. Vakrat, V. Brumfeld, E. Gabelmann, D. Leupold, J. R. Norris, H. Scheer and Y. Salomon (1998) Photosynthesis: Mechanisms and Effects, Vol. V (Edited by G. Garab), pp. 4207-4212. Kluwer Academic, Dordrecht.), probably as a result of a hydrogen bonding between the BChl macrocycle and the water molecules. In aprotic solvents, without hydrogen bonds, the permanent dipole moment of the first excited singlet state in both BChl and BChl-ser is increased compared with the ground state by at least 2.5 Debye.

Finesse and sensitivity gain in cavity-enhanced absorption spectroscopy of biomolecules in solution

“…An extrapolation from a linear fit to high-concentration single-pass measurements (αl) sp is also drawn in order to confirm the accuracy of our cavity-enhanced measurements. The extinction coefficient inferred from the latter measurements was ≈ 4.4 × 10 4 M −1 cm −1 , which is somewhat lower than the value of ≈ 6 × 10 4 (at 783 nm) that has been determined in more careful measurements [13]; we interpret this discrepancy to be an indication that the actual BChla concentration in our samples was somewhat lower than we assumed on the basis of the dopant/solvent ratio (the manufacturer designated the substance we used as 'partially purified' BChla). Aside from the linear behavior at high concentrations, the salient feature of our data plot is the flattening at low concentrations.…”

“…The BChla-doped d 6 -acetone sample is injected into the intracavity volume of a hermetically-sealed Fabry-Perot (FP) resonator (see below). A Verdi-pumped MBR-110 Titanium Sapphire laser (Ti:S) provides laser light at 783nm (cor-responding to the Q y transition in BChla, with expected extinction coefficient ≈ 6 × 10 4 M −1 cm −1 in acetone [13]; the Q y peak sits at 770nm but our Ti:S did not operate stably there with the mirror set we have) for probing the cavity response. The Ti:S laser is pre-stabilized to an internal reference cavity and an acousto-optic modulator (AO) driven by a voltage-controlled oscillator (VCO) is utilized to produce a frequency-shifted beam that can be locked to the FP (with 100 kHz bandwidth).…”

Synthesis of novel dimeric subphthalocyanines via azide-alkyne Huisgen 1,3-dipolar cycloaddition and palladiumcatalyzed Glaser–Hay coupling reactions

“…The singlet oxygen quantum yield (Φ D ) values of monomeric subphthalocyanines 2 and 3 were again found to be higher than their dimeric counterparts 4 and 5 due to the selfquenching of the subphthalocyanine rings. The studied subphthalocyanine derivatives (2-5) showed higher singlet oxygen generation in comparison with other photosensitizers such as bacteriochlorophyll a (Φ D = 0.35 in acetone [29]) and silicon(IV) naphthalocyanine (Φ D = 0.33 in DMF [30,31]). However, these subphthalocyanines showed lower singlet oxygen quantum yield values than other photosensitizers like benzoporphyrin derivative (BDP-MA) (Φ D = 0.76 in methanol [32]), chlorin-e 6 (Φ D = 0.65 in ethanol [33,34]), zinc tetraphenylporphyrin (Φ D = 0.73 in benzene [35,36]), and meso-tetra(4-methoxyphenyl) porphyrin (Φ D = 0.65 in THF [37]).…”

Spectral and photosensitizing properties of bacteriochlorin a and its monomethyl and dimethyl esters

“…Accordingly, BChl a and its derivatives are more promising for photodynamic therapy purposes because of their spectral characteristics. A series of BChl a derivatives (bacteriopheophorbid a [3,4], bacteriochlorin a (BCA) [5,6], bacteriopurpurin a [7,8], and also their conjugates with amino acids [1, 9,10]) exhibit high photodynamic activity in vivo and in vitro. In this case, we observe photodynamic effects with formation of both singlet molecular oxygen and radical products [5,6,11].…”