高效液相色谱-质谱联用测定婴幼儿配方奶粉中的左旋肉碱

建立了婴幼儿配方奶粉中左旋肉碱含量的高效液相色谱-质谱联用测定方法。采用C4色谱柱(4.6mm×250 mm,5μm)进行分离,以甲醇-水(10∶90)为流动相,柱温25℃,流速1.0 mL.min-1,进样量为10μL,柱后分流比为1∶3,质谱采用多离子反应监测(MRM)方式进行检测,正离子模式,定量离子为m/z 162.2→103.1。在优化条件下,样品在10 min内完成分析,左旋肉碱在0.40～10.0 mg.L-1范围内线性关系良好(r=0.999 3)。方法的加标回收率为87%～106%,检出限(S/N=3)和定量下限(S/N=10)分别为39.0、116.9 ng。该方法操作简便、灵敏度高、重复性好,可用于婴幼儿配方奶粉中左旋肉碱的测定。     

Preparation and Characterization of Al8.31Si1.91Mg3.78O20/Al4.8Si1.2O9.6/Mg2.0Al4.02Si4.98O18 Multiphase Material

A two-step sintering method was used to prepare Al8.31Si1.91Mg3.78O20 (corundum solid solution)/Al4.8Si1.2O9.6 (mullite solid solution)/Mg2.0Al4.02Si4.98O18 (cordierite solid solution) multiphase material, for the purposes of making these three crystal structures have point defects which could help the particles diffuse and transfer at high temperature, accelerate the sintering efficiently and enhance the material strength as well as the bulk density. The impacts of different formulas on the structure and properties of the multiphase material were investigated. With XRD and SEM analyses, for each sample, the crystal structure and microstructure were characterized, the crystalline phase content and cell parameters were determined with Rietveld Quantification software, and the properties were tested. The comparative optimal formula determined was calcinated chamotte of 80wt% and calcinated sludge of 20wt%; and its corresponding bending strength and retention rate of bending strength after a thermal shock were 29.74 MPa and 80.15%, respectively.     

超高效液相色谱法测定婴幼儿配方奶粉中的叶黄素

建立了采用超高效液相色谱测定婴幼儿配方奶粉中叶黄素的检测方法。样品经丙酮溶液提取,离心分层,冷冻离心去脂,YMC Carotenoid C30色谱柱（150 mm×4.6 mm,3 μm）分离。以甲醇-甲基叔丁基醚（70：30,v/v）为流动相等度洗脱,流速为0.5 mL/min,进样量5 μL,柱温25 ℃,二极管阵列检测器检测,检测波长445 nm。方法在20~500 μg/L范围内线性关系良好;相关系数为0.999 9;定量限为20 μg/L。添加量在50、250、2000 μg/kg时,叶黄素的回收率为97.9%~104.4%。本方法操作简便,结果准确,灵敏度高,适用于婴幼儿奶粉中叶黄素的测定。     

Synthesis,Biochemical Characterization,and Genetic Encoding of a 1,2,4-Triazole Amino Acid as an Acetyllysine Mimic for Bromodomains of the BET Family

Lysine acetylation is a charge-neutralizing post-translational modification of proteins bound by bromodomains (Brds). A 1,2,4-triazole amino acid (ApmTri) was established as acetyllysine (Kac) mimic recruiting Brds of the BET family in contrast to glutamine commonly used for simulating this modification. Optimization of triazole substituents and side chain spacing allowed BET Brd recruitment to ApmTri-containing peptides with affinities similar to native substrates. Crystal structures of ApmTri-containing peptides in complex with two BET Brds revealed the binding mode which mirrored that of Kac ligands. ApmTri was genetically encoded and recombinant ApmTri-containing proteins co-enriched BRD3(2) from cellular lysates. This interaction was blocked by BET inhibitor JQ1. With genetically encoded ApmTri, biochemistry is now provided with a stable Kac mimic reflecting charge neutralization and Brd recruitment, allowing new investigations into BET proteins in vitro and in vivo.     

A Versatile Strategy for Screening Custom-Designed Warhead-Armed Cyclic Peptide Inhibitors

Demand for peptide-based pharmaceuticals has been steadily increasing, but only limited success has been achieved to date. To expedite peptide-based drug discovery, we developed a general scheme for cell-based screening of cyclic peptide inhibitors armed with a user-designed warhead. We combined unnatural amino acid incorporation and split intein-mediated peptide cyclization techniques and integrated a yeast-based colorimetric screening assay to generate a new scheme that we call the custom-designed warhead-armed cyclic peptide screening platform (CWCPS). This strategy successfully discovered a potent inhibitor, CY5-6Q, that targets human histone deacetylase 8 (HDAC8) with a K_D value of 15 nM. This approach can be a versatile and general platform for discovering cyclic peptide inhibitors.     

结构相角二阶代数式的应用：Ⅱ.正交空间群二阶式及其应用

以作者在前文中提出的单相角二阶代数式的推导方法为依据,在完成三斜、单斜空间群推导结果的基础上,进而又完成了正交晶系59个空间群二阶式的推导,从而提供了低级晶系(三斜、单斜和正交)全部74个空间群的简明、完备的二阶代数式运算用表。对三个晶体结构进行了相角估算,结果较好。文中提出了代数法应用的新特点,即“一种类型相角可用多种二阶式求得,多种类型相角也可用一种二阶式求算”。     

一种计算液接电势的新方法*

依据液接电势达稳态时通过边界层的净电荷为零这一思想,提出了一种计算液接电势的新方法。对于3类液接电势的计算,特别是Lewis-Sargent公式与Henderson方程的推导,思路清晰易懂,避免了过往液接电势计算方法存在的一些问题。本文所提出的方法能够为液接电势相关内容的教学提供借鉴。     

Heavy‐Atom Tunneling Calculations in Thirteen Organic Reactions: Tunneling Contributions are Substantial,and Bell's Formula Closely Approximates Multidimensional Tunneling at ≥250 K

Multidimensional tunneling calculations are carried out for 13 reactions, to test the scope of heavy‐atom tunneling in organic chemistry, and to check the accuracy of one‐dimensional tunneling models. The reactions include pericyclic, cycloaromatization, radical cyclization and ring opening, and S_N2. When compared at the temperatures that give the same effective rate constant of 3×10⁻⁵ s⁻¹, tunneling accounts for 25–95 % of the rate in 8 of the 13 reactions. Values of transmission coefficients predicted by Bell's formula, κ_Bell , agree well with multidimensional tunneling (canonical variational transition state theory with small curvature tunneling), κ_SCT. Mean unsigned deviations of κ_Bell vs. κ_SCT are 0.08, 0.04, 0.02 at 250, 300 and 400 K. This suggests that κ_Bell is a useful first choice for predicting transmission coefficients in heavy‐atom tunnelling.     

固相萃取-液相色谱法测定婴幼儿配方乳粉中的游离核苷酸

该文建立了婴幼儿配方乳粉中5种游离核苷酸的检测方法。婴幼儿配方乳粉经乙二胺四乙酸二钠和氯化钠溶液提取,强阴离子（SAX）固相萃取柱净化,通过反相Atlantis T₃色谱柱分离,二极管阵列检测器检测,外标法定量。结果表明：方法抗干扰能力强、准确度高,尤其对羊奶粉净化效果好、分离度高。5种游离核苷酸在0.5~10 mg/L范围内线性关系良好（r≥0.999）;添加水平在0.05~0.50 g/kg时,回收率为91.1%~112%,相对标准偏差为2.3%~4.7%;检出限为0.0010~0.0015 g/kg,定量限为0.0030~0.0045 g/kg。对乳粉质控样品进行检测,结果与中位值比较的偏差在10%以内。该方法可为监管部门提供技术支持,为乳品行业健康发展提供保障。     

HPLC-MS/MS法测定婴幼儿配方乳粉中胆碱、左旋肉碱、牛磺酸与肌醇

建立了一种同时测定婴幼儿配方乳粉中4种可选择成分(胆碱、左旋肉碱、牛磺酸和肌醇)的高效液相色谱-串联三重四极杆质谱(HPLC-MS/MS)分析方法。样品经温水溶解后用亚铁氰化钾和乙酸锌沉淀蛋白,上清液过滤后采用HSS T3色谱柱分离,三重四极杆质谱仪检测,胆碱和左旋肉碱使用内标法定量,牛磺酸和肌醇使用外标法定量。在最优化条件下,胆碱和左旋肉碱在0.01~2.0 mg/L范围内,牛磺酸和肌醇在0.1~2.0 mg/L范围内呈良好的线性关系,相关系数均大于0.997;胆碱和左旋肉碱的检出限均为1.5 mg/kg,牛磺酸和肌醇的检出限均为15 mg/kg。4种化合物的回收率为87.5%~102.4%,相对标准偏差(RSD,n=6)为3.0%~7.3%。该方法灵敏度高、净化效果好、定量准确,适用于婴幼儿配方乳粉中胆碱、左旋肉碱、牛磺酸和肌醇的同时快速检测。