辐射诱导水溶液中血卟啉瞬态的形成。脉冲辐解研究。

Radiation-induced formation of haematoporphyrin-transients in aqueous solution. A pulse radiolysis study.

作者信息

Getoff N, Solar S

机构信息

Institute of Theoretical Chemistry and Radiation Chemistry, University of Vienna, Austria.

出版信息

Int J Radiat Biol. 1995 Jun;67(6):619-26. doi: 10.1080/09553009514550741.

DOI:10.1080/09553009514550741

PMID:7608625

Abstract

The radiation-induced formation of some haematoporphyrin (HP) transients in aqueous solution was studied by pulse radiolysis. The OH radicals attack HP (rate constant k = (1.3 +/- 0.2) x 10(10) dm3 mol-1 s-1) and the resulting transients decay with 2k = (2.5 +/- 0.2) x 10(8) dm3 mol-1 s-1. The spectrum of the HP-OH species shows several maxima in the range of 450-850 nm (epsilon 590 = 3880, epsilon 640 = 3850, epsilon 800 = 3670 dm3 mol-1 cm-1). k for one electron reduction of HP (radical anion, HP.-) was determined by a direct eaq- attack on HP (at pH 9.0, k = (1.6 +/- 0.2) x 10(10) dm3 mol-1 s-1) as well as by electron transfer from hydroxyisopropyl radicals to the substrate (at pH 8.6, k = (3.2 +/- 0.1) x 10(8), at pH 3.8, k = (4.0 +/- 0.2) x 10(8), and at pH 2.0, k = (2.1 +/- 0.1) x 10(9) dm3 mol-1 s-1). In slightly alkaline media (pH 8.6 - 9.5) the HP.- transients have main absorption bands at lambda < 450 and 640 nm (epsilon 660 = 7500 dm3 mol-1 cm-1), whereas at pH 2.0 they are at lambda < 430 and 640 nm (epsilon 640 = 8170 dm3 mol-1 cm-1) and 710 nm (epsilon 710 = 8500 dm3 mol-1 cm-1). The one-electron oxidation of HP (formation of HP.+, radical cation) was studied by means of N3. or SO4.- species as electron acceptors. Using N3. at pH 9.5 k (HP + N3.) = (3.2 +/- 0.2) x 10(9) and for the decay 2k = (3.5 x 0.3) x 10(8) dm3 mol-1 s-1 were determined; at pH 3.6, k = (HP + N3.) = (7.1 +/- 0.3) x 10(8) and 2k = (2.6 +/- 0.3) x 10(7) dm3 mol-1 s-1 were found. In the case of SO4.- at pH9.8 a buildup (5.6 +/- 0.3) x 10.7 dm3 mol-1 s-1) was obtained. The spectrum of the HP.+ transients at pH 9.6 possesses several maxima with epsilon 345 = 38,800, epsilon 450 = 2400, epsilon 595 = 2880, and epsilon 660 = 3300 dm3 mol-1 cm-1. The corresponding values at pH 3.8 are epsilon 640 = 2450, epsilon 710 = 2600, and epsilon 780 = 1580 dm3 mol-1 cm-1.(ABSTRACT TRUNCATED AT 400 WORDS)

摘要

通过脉冲辐解研究了水溶液中辐射诱导形成的一些血卟啉（HP）瞬态。羟基自由基攻击HP（速率常数k = (1.3 ± 0.2) × 10¹⁰ dm³ mol⁻¹ s⁻¹），生成的瞬态以2k = (2.5 ± 0.2) × 10⁸ dm³ mol⁻¹ s⁻¹的速率衰减。HP-OH物种的光谱在450 - 850 nm范围内有几个最大值（ε₅₉₀ = 3880，ε₆₄₀ = 3850，ε₈₀₀ = 3670 dm³ mol⁻¹ cm⁻¹）。通过水合电子对HP的直接攻击（在pH 9.0时，k = (1.6 ± 0.2) × 10¹⁰ dm³ mol⁻¹ s⁻¹）以及羟基异丙基自由基向底物的电子转移（在pH 8.6时，k = (3.2 ± 0.1) × 10⁸，在pH 3.8时，k = (4.0 ± 0.2) × 10⁸，在pH 2.0时，k = (2.1 ± 0.1) × 10⁹ dm³ mol⁻¹ s⁻¹）测定了HP单电子还原（自由基阴离子，HP⁻）的k值。在微碱性介质（pH 8.6 - 9.5）中，HP⁻瞬态在λ < 450和640 nm处有主要吸收带（ε₆₆₀ = 7500 dm³ mol⁻¹ cm⁻¹），而在pH 2.0时，它们在λ < 430和640 nm处（ε₆₄₀ = 8170 dm³ mol⁻¹ cm⁻¹）以及710 nm处（ε₇₁₀ = 8500 dm³ mol⁻¹ cm⁻¹）。通过使用N₃⁻或SO₄⁻⁻物种作为电子受体研究了HP的单电子氧化（HP⁺的形成，自由基阳离子）。在pH 9.5时使用N₃⁻，测定k(HP + N₃⁻) = (3.2 ± 0.2) × 10⁹，其衰减2k = (3.5 × 0.3) × 10⁸ dm³ mol⁻¹ s⁻¹；在pH 3.6时，k(HP + N₃⁻) = (7.1 ± 0.3) × 10⁸，2k = (2.6 ± 0.3) × 10⁷ dm³ mol⁻¹ s⁻¹。在pH 9.8时使用SO₄⁻⁻，得到积累速率为(5.6 ± 0.3) × 10⁷ dm³ mol⁻¹ s⁻¹。pH 9.6时HP⁺瞬态的光谱有几个最大值，ε₃₄₅ = 38800，ε₄₅₀ = 2400，ε₅₉₅ = 2880，ε₆₆₀ = 3300 dm³ mol⁻¹ cm⁻¹。pH 3.8时的相应值为ε₆₄₀ = 2450，ε₇₁₀ = 2600，ε₇₈₀ = 1580 dm³ mol⁻¹ cm⁻¹。（摘要截断于400字）