Velthuys B R, Amesz J
Biophysical Laboratory of the State University, P.O. Box 556, Leiden, The Netherlands.
Biochim Biophys Acta. 1974 Jan 18;333(1):85-94. doi: 10.1016/0005-2728(74)90165-0.
A study was made of the reactions between the primary and secondary electron acceptors of Photosystem 2 by measurements of the increase of chlorophyll fluorescence induced in darkness by dithionite or by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). The experiments were done either with chloroplasts to which hydroxylamine or carbonylcyanide-p-trifluoromethoxyphenylhydrazone (FCCP) was added, or with chloroplasts treated with tris(hydroxymethyl)aminomethane (Tris) to which phenylenediamine and ascorbate were added as donor system. Under these conditions the fluorescence increase induced by dithionite or DCMU added after illumination with short light flashes was dependent on the flash number with a periodicity of two; it was large after an uneven number of flashes, and small after a long darktime or after an even number of flashes. The results are interpreted in terms of a model which involves a hypothetical electron carrier situated between Q and plastoquinone; this electron carrier is thought to equilibrate with plastoquinone in a two-electron transfer reaction; the results obtained with DCMU are explained by assuming that its midpoint potential is lowered by this inhibitor.
通过测量连二亚硫酸盐或3-(3,4-二氯苯基)-1,1-二甲基脲（DCMU）在黑暗中诱导的叶绿素荧光增加，对光系统2的初级和次级电子受体之间的反应进行了研究。实验是在添加了羟胺或羰基氰化物-对-三氟甲氧基苯腙（FCCP）的叶绿体上进行的，或者是在添加了苯二胺和抗坏血酸作为供体系统的经三（羟甲基）氨基甲烷（Tris）处理的叶绿体上进行的。在这些条件下，短闪光照射后添加连二亚硫酸盐或DCMU诱导的荧光增加取决于闪光次数，周期为2；奇数闪光后荧光增加较大，长时间黑暗后或偶数闪光后荧光增加较小。结果用一个模型来解释，该模型涉及一个位于Q和质体醌之间的假设电子载体；这个电子载体被认为在双电子转移反应中与质体醌达到平衡；用DCMU获得的结果通过假设其中点电位被这种抑制剂降低来解释。
