化学
生物分子
稳定同位素比值
分馏
热力学平衡
同位素
基质(化学分析)
同位素分馏
生物系统
热力学
色谱法
生物化学
物理
量子力学
生物
作者
Yuyang He,Xiaobin Cao,Jianwei Wang,Huiming Bao
摘要
Rationale Although being out of equilibrium, biomolecules in organisms have the potential to approach isotope equilibrium locally because enzymatic reactions are intrinsically reversible. A rigorous approach that can describe isotope distribution among biomolecules and their apparent deviation from equilibrium state is lacking, however. Methods Applying the concept of distance matrix in graph theory, we propose that apparent local isotope equilibrium among a subset of biomolecules can be assessed using an apparent fractionation difference (|Δα|) matrix, in which the differences between the observed isotope composition (δ') and the calculated equilibrium fractionation factor (1000lnβ) can be more rigorously evaluated than by using a previous approach for multiple biomolecules. We tested our |Δα| matrix approach by re‐analyzing published data of different amino acids (AAs) in potato and in green alga. Results Our re‐analysis shows that biosynthesis pathways could be the reason for an apparently close‐to‐equilibrium relationship inside AA families in potato leaves. Different biosynthesis/degradation pathways in tubers may have led to the observed isotope distribution difference between potato leaves and tubers. The analysis of data from green algae does not support the conclusion that AAs are further from equilibrium in glucose‐cultured green algae than in the autotrophic ones. Conclusions Application of the |Δα| matrix can help us to locate potential reversible reactions or reaction networks in a complex system such as a metabolic system. The same approach can be broadly applied to all complex systems that have multiple components, e.g. geochemical or atmospheric systems of early Earth or other planets.
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