Kallas T, Dahlquist F W
Biochemistry. 1981 Sep 29;20(20):5900-7. doi: 10.1021/bi00523a038.
Phosphorus-31 nuclear magnetic resonance (31P NMR) spectra were obtained from actively photosynthesizing and darkened suspensions of the unicellular cyanobacterium Synechococcus. These spectra show intracellular resonances belonging to inorganic phosphate (Pi), a sugar phosphate (sugar-P), nucleotide di- and triphosphates, and poly-phosphates. The pH-dependent chemical shifts of Pi and sugar-P allowed the estimation of intracellular pH. When irradiated with high-intensity tungsten-halogen light (100 x 10(4) ergs . cm-2 . s-1, measured in the visible range), concentrated cell suspensions in the NMR spectrometer incorporated NaH14CO3 at approximately two-thirds the rate shown by a dilute suspension of cells at saturating light intensity. On the basis of NaH14CO3 incorporation, the effective light intensity obtained under NMR conditions would support growth at approximately one-fourth the maximum rate in dilute suspensions of cells. Irradiated cells maintained a cytoplasmic pH of 7.1--7.3 when exposed to an external pH from 6.4 to 8.3. At an external pH of 6.7, a darkness to light shift caused a 0.4 pH unit alkalinization of the cytoplasm. Treatment of cell suspensions with the uncoupler, carbonyl cyanide m-chlorophenylhydrazone (CCCP), in light or darkness, collapsed the internal pH to the level of the external pH. The results suggest a strong light- or energy-dependent buffering of the cytoplasm over a range of external pH. The study demonstrates that 31P NMR can be used to investigate intracellular events in an actively photosynthesizing microorganism.
从单细胞蓝藻聚球藻的活跃光合作用悬浮液和黑暗悬浮液中获得了磷-31核磁共振（31P NMR）光谱。这些光谱显示了属于无机磷酸盐（Pi）、磷酸糖（糖-P）、核苷酸二磷酸和三磷酸以及多磷酸盐的细胞内共振峰。Pi和糖-P的pH依赖性化学位移使得能够估算细胞内pH值。当用高强度钨卤灯照射（在可见光范围内测量为100×10⁴尔格·厘米⁻²·秒⁻¹）时，核磁共振光谱仪中的浓缩细胞悬浮液掺入NaH¹⁴CO₃的速率约为饱和光强下稀细胞悬浮液所示速率的三分之二。基于NaH¹⁴CO₃的掺入情况，在核磁共振条件下获得的有效光强将支持细胞以约为稀细胞悬浮液中最大生长速率四分之一的速度生长。当暴露于6.4至8.3的外部pH值时，受照射细胞的细胞质pH值维持在7.1 - 7.3。在外部pH值为6.7时，从黑暗到光照的转变导致细胞质碱化0.4个pH单位。在光照或黑暗条件下，用解偶联剂羰基氰化物间氯苯腙（CCCP）处理细胞悬浮液，会使内部pH值降至外部pH值水平。结果表明，在一系列外部pH值范围内，细胞质存在强烈的光或能量依赖性缓冲作用。该研究表明，31P NMR可用于研究活跃光合作用微生物中的细胞内事件。
