共查询到20条相似文献,搜索用时 265 毫秒
1.
2.
以廉价的外消旋乳酸(D,L-LA)为原料,胆酸为核,氧化亚锡为催化剂,采用熔融聚合法合成了星型结构的胆酸-聚(D,L-乳酸)共聚物,分别考察了预聚时间、催化剂种类、用量以及熔融共聚时间等的影响,并用FT-IR、1HNMR、GPC等对共聚物进行了表征。当胆酸和乳酸的投料比(以物质的量计)为1∶64、预聚8h、熔融共聚8h、熔融温度160℃、催化剂用量0.3%时,以51.9%的产率生成了重均分子量(Mw)达5600(分散度Mw/Mn=1.37)的共聚物。分析表明,每个星型结构高分子中含有一个胆酸单元核心。本方法步骤少,有利于该类含特殊功能基团的药物缓释材料的廉价、快速合成。 相似文献
3.
4.
采用高效液相色谱法测定了药用辅料聚L乳酸中乳酸单体的残留量。采用正交试验优化了色谱的条件,以甲醇-0.1mol.L磷酸二氢钾(5+95)混合液为流动相,流量为0.8mL.min-1,柱温为40℃。乳酸的质量浓度在2.00~100mg·L-1范围内与其峰高呈线性关系,方法的检出限(3S/N)为0.50mg·L-1。对方法进行了回收率和精密度试验,样品的加标平均回收率为96%;测定值的相对标准偏差(n=6)为2.0%。 相似文献
5.
6.
7.
8.
以辛酸亚锡为催化剂,通过开环聚合法制备了聚左旋乳酸-三亚甲基碳酸酯(PLLA-TMC)和聚右旋乳酸-三亚甲基碳酸酯(PDLA-TMC)无规共聚物.利用共聚物中PLLA/PDLA链段形成立构复合体,通过溶液浇注法制备了PLLA-TMC/PDLA-TMC立构复合聚乳酸材料(sc-PLA-TMC).研究结果表明,聚合物链中的柔性TMC单元可以增强L(D)LA链段的运动能力,有助于不同旋光性的LA链段形成立构复合晶体,但也使得L(D)LA链段的规整度和序列长度降低.即随着共聚物链段中柔性TMC单元摩尔含量的增加,sc-PLA-TMC中同质结晶能力降低.当TMC含量≥5%时,仅生成熔点200℃的PLLA/PDLA立构复合结晶,表明sc-PLA-TMC的耐热性有所提高.蛋白酶K降解实验表明,PL(D)LA-TMC共聚物的降解速率不但比PLLA高,而且可通过共聚物中TMC含量进行调控. 相似文献
9.
目前生物可降解塑料主要采用堆肥降解测定其生物降解性能的方法进行鉴别,其检测周期长、费用较高。材料的组成基本决定了其生物降解特性,为了快速鉴别生物可降解塑料,采用热裂解-气相色谱-质谱法(PY-GC-MS)对以聚对苯二甲酸-己二酸丁二醇酯(PBAT)与不同质量比的其他成分包括生物可降解聚乳酸(PLA)、难降解材料聚苯乙烯(PS)或聚对苯二甲酸乙二醇酯(PET)混合样的裂解特征进行了研究。结果显示,PBAT的裂解特征峰明显,未受到PLA的影响;若在PBAT中添加质量分数1%的非降解材质PS和PET也可被检出。方法用于市场上收集到的标识为可降解塑料购物袋样品的分析,结果表明,采用PY-GC-MS可以快速对可降解塑料进行初步鉴别。 相似文献
10.
11.
Shinobu Honzawa Naoyuki Takahashi Takayuki Sugiura Midori A. Arai Shigeaki Kato 《Tetrahedron》2009,65(34):7135-7145
Vitamin D3 analogues have been developed for a mutant vitamin D receptor (VDR), Arg274Leu. The mutant VDR has a mutation at Arg274, which forms an important hydrogen bond with 1α-OH of 1α,25-dihydroxyvitamin D3 to anchor the ligand tightly in the VDR ligand binding pocket. Stereoselective synthesis of the A-ring part of the novel vitamin D analogue, 2α-(3-hydroxypropyl)-1α-methyl-25-hydroxyvitamin D3 (4), from d-galactose was accomplished with the key steps of the introduction of the methyl and allyl groups to the chiral building blocks. The new analogue 4 is ca. 7.3-fold more active than the natural hormone 1α,25-dihydroxyvitamin D3 (1). 相似文献
12.
维生素D包合物中维生素D的高效液相色谱测定 总被引:2,自引:2,他引:0
Vitamin D in the VDHCD inclusion complex was determined by HPLC on a Resolve silica column usingamobile phase of n-hexane:n-amylalcohol=95:5(V/V)and UV detection at 254 nm.The quantitative de-termination was performed with dimethyl phthalate as the internal standard. 相似文献
13.
基于Boentgen、Laue与Ewald、W.H.Bragg及W.L.Bragg、Friedrich和Knipping等前辈X射线及其晶体学的研究与发现,X射线晶体结构分析已成为研究原子或离子在晶体点阵中结合、鉴定晶体化合物空间结构的可靠方法.Debye-Scherrer粉晶X射线衍射法(XRPD)在合成氨装置101D工况技术分析中,比较有意义的实际应用是解决由不同单质或化合物组成的复杂混合堵塞物中晶体的鉴定问题.采用XRPD定性分析了合成氨装置101D堵塞物样品中的主要晶体成分.实验结果表明:本法对合成氨装置101D工况技术分析具有重要的意义. 相似文献
14.
提出了用反相高效液相色谱法(RP-HPLC)分离和测定胶囊、油状试剂中维生素D2及维生素D3的含量。样品用甲醇超声提取,提取液用甲醇定容至100mL,经0.45μm滤膜过滤后供HPLC分析。采用Zorbax SB-C18反相色谱柱及C18保护柱作为分离柱,乙腈作为流动相,流量为1.0mL.min-1,在波长265nm处作紫外检测,进样量为20μL。维生素D2和维生素D3的质量浓度在0.50~20mg.L-1范围内与相应的峰面积呈线性关系,测得检出限(3S/N)依次为0.030,0.026mg.L-1。此方法应用于实样分析并在此基础用标准加入法做回收试验,同时进行精密度试验,测得回收率在95.0%~99.4%之间,测定值的相对标准偏差(n=6)在1.2%~2.6%之间。 相似文献
15.
Although ultrasonography is an important cost-effective imaging modality, technical improvements are needed before its full potential is realized for accurate and reproducible monitoring of disease progression or regression. Two-dimensional viewing of three-dimensional anatomy, using conventional ultrasonography, limits our ability to quantify and visualize pathology and is partly responsible for the reported variability in diagnosis and monitoring of disease progression. Efforts of investigators have focused on overcoming these deficiencies by developing 3D ultrasound imaging techniques that are capable of acquiring B-mode images using existing conventional ultrasound systems, reconstructing the information into 3D images, and then allowing interactive viewing of the 3D images on inexpensive desktop computers. In addition, the availability of 3D ultrasound images has allowed the development of manual and semi-automated techniques to quantify normal and abnormal anatomical volumes. In this paper we review our semi-automated 3D segmentation approaches for segmenting the surface of the carotid arteries and plaques, and segmenting the prostate. These techniques demonstrate that efficient segmentation techniques can be used with 3D ultrasound images to quantify anatomical organ volumes and morphology. 相似文献
16.
Muhammad Imran Muhammad Ibrahim Naheed Riaz Prof. Dr. Abdul Malik 《Magnetic resonance in chemistry : MRC》2009,47(6):532-536
Aervins A‐D (1‐4), four new coumaronochromone analogues have been isolated from the CHCl3‐soluble fraction of the MeOH extract of the whole plant of Aerva persica. Their structures were assigned based on 1H NMR, 13C NMR spectra, DEPT, and by 2DNMR experiments. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
17.
18.
Ju Cheol Son Dong Woo Kang Kwang Mo Yang Kang-Yell Choi Tae Gen Son Do Sik Min 《Experimental & molecular medicine》2013,45(8):e38
Radiation and drug resistance remain the major challenges and causes of mortality in the treatment of locally advanced, recurrent and metastatic breast cancer. Dysregulation of phospholipase D (PLD) has been found in several human cancers and is associated with resistance to anticancer drugs. In the present study, we evaluated the effects of PLD inhibition on cell survival, cell death and DNA damage after exposure to ionizing radiation (IR). Combined IR treatment and PLD inhibition led to an increase in the radiation-induced apoptosis of MDA-MB-231 metastatic breast cancer cells. The selective inhibition of PLD1 and PLD2 led to a significant decrease in the IR-induced colony formation of breast cancer cells. Moreover, PLD inhibition suppressed the radiation-induced activation of extracellular signal-regulated kinase and enhanced the radiation-stimulated phosphorylation of the mitogen-activated protein kinases p38 and c-Jun N-terminal kinase. Furthermore, PLD inhibition, in combination with radiation, was very effective at inducing DNA damage, when compared with radiation alone. Taken together, these results suggest that PLD may be a useful target molecule for the enhancement of the radiotherapy effect. 相似文献
19.
Two new vitamin D2 analogues, (22Z)-25-(OH)-D2 and (22Z)-1α,25-(OH)2-D2, were serendipitously synthesized from vitamin D2 and using the Julia-Kocienski olefination. 相似文献
20.
《中国化学快报》2021,32(10):3226-3230
Low dimension nano photocatalysts show great potential in the field of treating contaminated water for their large surface area and size effect. In this study, a 0D/1D AgI/MoO3 Z-scheme photocatalyst with striking photocatalytic performance was constructed successfully. The one-dimensional MoO3 nanobelts were prepared by a simple hydrothermal method, and then it was modified by AgI nanoparticles in a handy deposition approach. When choosing sulfamethoxazole (SMZ) as the target contaminant, the rate constant value of the optimal 0D/1D AgI/MoO3 composite could hit up to 0.13 min−1, which is nearly 22.4 times and 32.5 times as that of pure MoO3 (0.0058 min−1) and AgI (0.0040 min−1), respectively. A series of detailed characterizations give evidences that the charge transfer in the composite followed Z scheme mechanism. Therefore, efficient separation/transfer and the remained high redox activity of photogenerated carriers played a vital role in the sharply enhanced photocatalytic properties. The possible degradation pathways of SMZ were proposed based on the intermediates detected by high-performance liquid chromatography-mass spectrometry (HPLC-MS). Meanwhile, the magnificent cyclic stability makes the material a promising material in the practical application. 相似文献