A paramagnetic Cys₄[Fe] center was detected by pulse EPR in Na⁺-translocating NADH:quinone-oxidoreductase (Na⁺-NQR) by influence of this center on transverse and longitudinal spin relaxation of Na⁺-NQR flavin radicals. The oxidation state of the Cys₄[Fe] center was Fe³⁺ in the oxidized and Fe²⁺ in the reduced Na⁺-NQR, as deduced from the temperature dependence of spin relaxation rates of different flavin radicals. A high-spin state of iron in the Cys₄[Fe] center was assigned to both forms of Na⁺-NQR.

中文翻译：

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EPR证据表明，Na ^+-易位的NADH：醌氧化还原酶中的铁中心快速松弛

通过脉冲EPR在Na ⁺ -易位的NADH：醌-氧化还原酶（Na ⁺ -NQR）中检测到顺磁性的Cys ₄ [Fe]中心，该中心对Na ⁺ -NQR黄素自由基的横向和纵向自旋弛豫有影响。Cys ₄ [Fe]中心的氧化态为氧化态的Fe ³⁺和还原的Na ⁺ -NQR中的Fe ²⁺，这是根据不同黄素自由基的自旋弛豫速率对温度的依赖性推导的。Cys ₄ [Fe]中心的铁的高自旋态被指定为Na ⁺ -NQR的两种形式。