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Fluorescence Assay for Tolyporphins Amidst Abundant Chlorophyll in Crude Cyanobacterial Extracts
Photochemistry and Photobiology ( IF 2.6 ) Pub Date : 2021-06-21 , DOI: 10.1111/php.13474
Kathy-Uyen Nguyen 1 , Ran Zhang 1 , Masahiko Taniguchi 1 , Jonathan S Lindsey 1
Affiliation  

Tolyporphins are distinctive tetrapyrrole natural products found singularly in a filamentous cyanobacterial-microbial holobiont (termed HT-58-2) from Micronesia. The absorption and fluorescence features of tolyporphins resemble those of chlorophyll a, complicating direct analysis of culture samples. Treatment of the crude (unfractionated) organic extract (CH2Cl2/2-propanol, 1:1) of HT-58-2 cultures with NaBH4 in methanol causes reduction of the peripheral ketone auxochromes, whereupon tolyporphins (predominantly 7,17-dioxobacteriochlorins) exhibit a bathochromic shift (λabs ˜ 676 → ˜ 700 nm) and chlorophyll a (a 131-oxochlorin) exhibits a hypsochromic shift (λabs 665 → 634 nm). Fluorescence excitation spectroscopy (at 368 and 491 nm with λem 710 nm) enabled detection of reduced tolyporphins amidst abundant reduced chlorophyll a (1:19 ratio), a detection sensitivity >5 times that without reduction. The resulting assay combines simple sample preparation from non-axenic cultures at microscale quantities (2 mL, 2 μm), absence of any fractionation procedures, and fluorescence detection. Tolyporphins were readily detected in cultures of HT-58-2 at reasonable growth periods in the absence of environmental stressors, which was not possible previously.

中文翻译:

粗蓝藻提取物中富含叶绿素中甲苯卟啉的荧光测定

Tolyporphins 是独特的四吡咯天然产物,在密克罗尼西亚的丝状蓝藻微生物全生物(称为 HT-58-2)中发现。Tolyporphins 的吸收和荧光特征类似于叶绿素a的吸收和荧光特征,使培养样品的直接分析变得复杂。用甲醇中的 NaBH 4处理 HT-58-2 培养物的粗(未分级)有机提取物(CH 2 Cl 2 /2-丙醇,1:1)导致外周酮辅助色素减少,因此甲苯卟啉(主要是 7,17 -dioxobacteriochlorins) 表现出红移 ( λ abs ~ 676 → ~ 700 nm) 和叶绿素a (a 13 1-oxochlorin) 表现出低色移 ( λ abs 665 → 634 nm)。荧光激发光谱(在 368 和 491 nm,λ em 710 nm)能够在大量还原的叶绿素a(1:19 比例)中检测还原的甲苯卟啉,检测灵敏度 > 5 倍于不还原。由此产生的测定结合了从非无菌培养物中以微量(2 mL,2 μ m)进行的简单样品制备,没有任何分级程序,以及荧光检测。在没有环境压力源的情况下,在合理的生长期,HT-58-2 培养物中很容易检测到 Tolyporphins,这在以前是不可能的。
更新日期:2021-06-21
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