HSQC spectra of lignin isolated from poplar roots

Here we present a curated dataset of two-dimensional heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectra of lignin isolated from roots of a greenhouse grown natural population of an energy crop poplar (Populus trichocarpa). Dormant cuttings of field-grown poplar were grown in 6-liter pots in a peat-based media containing bark, perlite, vermiculite, dolomite lime and a wetting agent in an environmentally controlled greenhouse. Temperatures were between 21 and 23 °C, with supplemental lighting to support a 16-h day length using 1000-watt high-pressure sodium lights in greenhouse. Once established, all plants were cut-back, allowed to regrow and harvested at the same time following an eight-month long growth period. Plants were harvested and the belowground roots were washed off soils, blotted, dried in an oven at 70 °C for 3 days, and Wiley milled (mesh size 20). The roots were Soxhlet-extracted with toluene/ethanol for 24 h to remove extractives. The extracted roots were ball-milled in a Retsch PM100 planetary ball mill using a porcelain jar with ceramic balls at 600 rpm for 2 h (in 5 min on and 5 min off cycles to avoid excessive sample heating). The ball-milled materials were then subjected to enzymatic hydrolysis for 48 h followed by centrifugation and washing with deionized water. The solid residue was extracted twice with 96% (v/v) 1,4-dioxane/water mixture at room temperature overnight. The extracts were combined, rotary evaporated, and freeze-dried to recover lignin. The dry lignin samples were dissolved in deuterated dimethyl sulfoxide (d6) and transferred into a 5 mm tube. 13C–1H HSQC experiments were performed in a Bruker Avance III HD 500 MHz NMR spectrometer operating at a frequency of 125.12 MHz for the 13C nucleus using a standard Bruker pulse sequence on a Prodigy platform cryoprobe. The NMR spectra were acquired under the following acquisition conditions: 220 ppm spectral width in F1 (13C) dimension with 256 data points and 12 ppm spectral width in F2 (1H) dimension with 1024 data points, a 90° pulse, a one bond C–H coupling constant of 145 Hz, a 1.0 s pulse delay, and 64 scans. Spectra were processed using the Bruker TopSpin software. Additional meta data is embedded in the raw spectra figures.

本研究公开一套精心筛选的二维异核单量子相干（HSQC）核磁共振（NMR）光谱数据集，样品为从温室种植的能源作物毛果杨（Populus trichocarpa）自然种群根系中分离得到的木质素。将田间采集的毛果杨休眠插条种植于6升容积的花盆中，栽培基质为含树皮、珍珠岩、蛭石、白云石石灰及润湿剂的泥炭基基质，栽培于环境可控温室中。温室温度维持在21~23 ℃，采用1000瓦高压钠灯提供补光，以维持16小时的光照时长。植株定植后进行截干处理，待其重新萌发后，经过8个月的生长周期统一采收。采收后将地下根系洗净泥土、吸干水分，于70 ℃烘箱中干燥3天，随后经韦斯利粉碎机（Wiley mill）以20目筛网粉碎。将粉碎后的根系采用甲苯/乙醇混合溶剂进行索氏提取24小时，以去除可溶性提取物。提取后的根系样品置于Retsch PM100型行星式球磨机中，使用陶瓷罐与陶瓷球，以600转每分钟的转速球磨2小时（采用5分钟运转、5分钟暂停的循环模式，避免样品过热）。球磨后的物料随后进行48小时酶解，接着经离心、去离子水洗涤后收集固体残渣。将固体残渣用96%（体积比）1,4-二氧六环/水混合液在室温下萃取两次，每次过夜。合并萃取液，经旋转蒸发、冷冻干燥后得到目标木质素样品。将干燥的木质素样品溶解于氘代二甲基亚砜（deuterated dimethyl sulfoxide, d6），转移至5毫米核磁管中。使用布鲁克（Bruker）Avance III HD 500兆赫兹核磁共振波谱仪，搭配Prodigy系列低温探头，采用标准布鲁克脉冲序列，对13C核以125.12兆赫兹的频率开展13C-1H异核单量子相干实验。核磁光谱采集参数如下：F1维度（13C核）谱宽220 ppm，数据点数256；F2维度（1H核）谱宽12 ppm，数据点数1024；90°脉冲，一键C-H耦合常数145 Hz，脉冲延迟1.0秒，扫描次数64次。光谱数据采用布鲁克TopSpin软件进行处理。原始光谱图中嵌入了额外的元数据。