Enhanced extracellular production of alpha-lactalbumin from Bacillus subtilis through signal peptide and promoter screening

Alpha-lactalbumin(α-LA)is a major whey protein found in breast milk and plays a crucial role in the growth and development of infants.In this study,Bacillus subtilis RIK1285 harboring AprE signal peptide(SP)was selected as the original strain for the production ofα-LA.It was found thatα-LA was identified in the pellet after ultrasonic disruption and centrifugation instead of in the fermentation supernatant.The original strain most likely only producedα-LA intracellular,but not extracellular.To improve the expression and secretion ofα-LA in RIK1285,a library of 173 homologous SPs from the B.subtilis 168 genome was fused with target LALBA gene in the pBE-S vector and expressed extracellularly in RIK1285.SP YjcN was determined to be the best signal peptide.Bands in supernatant were observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and purified by nickel column to calculate the highest yield signal peptide.In addition,different promoters(P_(aprE),P_(43),and P_(glv))were compared and applied.The results indicated that the strain RIK1285-pBE-P_(glv)-YjcN-LALBA had the highestα-LA yield,reaching 122.04μg/mL.This study demonstrates successful expression and secretion of humanα-LA in B.subtilis and establishes a foundation for simulating breast milk for infant formulas and developing bioengineered milk.

Protective effects of peptide KSPLY derived from Hericium erinaceus on H_(2)O_(2)-induced oxidative damage in HepG2 cells

Reactive oxygen species(ROS)-induced oxidative damage is strongly associated with the pathogenesis of chronic diseases,and natural antioxidant peptides have good abilities of scavenging ROS.The antioxidant activity of peptide Lys-Ser-Pro-Leu-Tyr(KSPLY)derived from Hericium erinaceus remains unclear.In the present study,the antioxidant effect and mechanism of KSPLY on H_(2)O_(2)-induced oxidative damage in HepG2 cells were investigated.The results indicated that KSPLY exhibited the antioxidant capacity in H_(2)O_(2)-induced HepG2 cells by enhancing superoxide dismutase(SOD),glutathione peroxidase(GSH-Px),and catalase(CAT)activities.In comparison with the H_(2)O_(2)-treated damage group,the apoptosis rate,ROS level,and malondialdehyde(MDA)content of HepG2 cells treated with KSPLY were significantly decreased.The H.erinaceus-derived peptide KSPLY pretreatment promoted the expression of detoxification and antioxidant enzymes via the Keap1/Nrf2 signal pathway,thereby inhibiting the generation of ROS and MDA.In conclusion,the H.erinaceus-derived peptide KSPLY effectively protected HepG2 cells against H_(2)O_(2)-induced oxidative damage,and it provided a theoretical basis for the further development of new natural antioxidants.

Computational Analysis of Signal Peptide-Dependent Secreted Proteins in Saccharomyces cerevisiae

Computer based software such as the SignalP v3.0, TargetP v1.01, big-PI predictor and TMHMM v2.0 were combined to predict the signal peptides, and the signal peptide-dependent secreted proteins among the 6 700 ORFs in genome of Saccharomyces cerevisiae. The results showed that 163 proteins were the secreted ones containing signal peptides, and they were secreted via Sec pathway. Among the 163 predicted secreted proteins, the signal peptides of 47 secreted proteins included only the H-domain and C-domain, without N-domain, but the signal peptides of other 116 secreted proteins included all the three domains. There were differences in the constitution of signal peptides between the secreted proteins of S. cerevisiae and of Candida albicans, but the length and amino acids types of their signal peptides were similar in general. Few of the same signal peptides occurred in the secreted proteins of S. cerevisiae genome, and the homology could be compared among the secreted proteins with the same signal peptides. The BLAST 2 SEQUENECES and CLUSTAL W were used to align the two protein sequences and multi-protein sequences, respectively. The alignment result indicated that homology of these sequences with the same signal peptide was very highly conservative in amino acid of complete gene. The effect of the signal peptides in S. cerevisia on expression of foreign eukaryotic secreted proteins is discussed in this paper.

Novel soybean peptide iglycin ameliorates insulin resistance of high-fat diet fed C57BL/6J mice and differentiated 3T3L1 adipocytes with improvement of insulin signaling and mitochondrial function

Soy consumption has been associated with potential health benefits in reducing chronic diseases.These physiological functions have been attributed to soy proteins or more commonly to bioactive peptides.Thus,more studies are required to identify these bioactive peptides,and elucidate their biological mechanisms of action.In the present study,a novel peptide iglycin was purifi ed from soybean seeds with a molecular mass of 3.88 k Da.Thereafter,iglycin reduced fasting blood glucose and restored insulin sensitivity of C57 BL/6 J mice on a high-fat diet with increased phosphorylation of insulin receptor substrate 1(IRS1)and AKT in adipose tissue.Furthermore,it improved glucose uptake,induced translocation of intracellular GLUT4 to plasma membrane and activation of insulin signaling in adipocytes under insulin-resistant condition.In addition,it decreased reactive oxygen species production,lipid peroxidation and inhibited adipocyte apoptosis with improved mitochondrial function as evidenced by up-regulation of succinate dehydrogenase activity,mitochondrial membrane potential and intracellular ATP store.These data suggested that iglycin ameliorated insulin resistance via activation of insulin signaling,which was associated with inhibition of oxidative stress,adipocyte apoptosis,and improvement of mitochondrial function.

A new peptide,VD11,promotes structural and functional recovery after spinal cord injury

The regenerative capacity of the central nervous system is very limited and few effective treatments are currently available for spinal cord injury.It is therefore a priority to develop new drugs that can promote structural and functional recovery after spinal cord injury.Previous studies have shown that peptides can promote substantial repair and regeneration of injured tissue.While amphibians have a pronounced ability to regenerate the spinal cord,few studies have investigated the effect of amphibian spinal cord-derived peptides on spinal cord injury.Here we report for the first time the successful identification and isolation of a new polypeptide,VD11(amino acid sequence:VDELWPPWLPC),from the spinal cord of an endemic Chinese amphibian(Odorrana schmackeri).In vitro experiments showed that VD11 promoted the secretion of nerve growth factor and brain-derived neurotrophic factor in BV2 cells stimulated with lipopolysaccharide,as well as the proliferation and synaptic elongation of PC12 cells subjected to hypoxia.In vivo experiments showed that intravertebral injection of VD11 markedly promoted recovery of motor function in rats with spinal cord injury,alleviated pathological damage,and promoted axonal regeneration.Furthermore,RNA sequencing and western blotting showed that VD11 may affect spinal cord injury through activation of the AMPK and AKT signaling pathways.In summary,we discovered a novel amphibian-derived peptide that promotes structural and functional recovery after spinal cord injury.

The protective effects of peptides from Chinese baijiu on AAPH-induced oxidative stress in HepG2 cells via Nrf2 signaling pathway

Antioxidant peptides have been widely reported.However,only a few reports have been published examining the antioxidant peptides derived from Chinese baijiu.In this study,6 novel peptides derived from Chinese baijiu were identified successfully using high-performance liquid chromatography-quadrupoletime-of-flight mass spectrometry(HPLC-QTOF-MS)with a concentration of 0.835–24.540μg/L.The underlying molecular mechanisms were investigated,and their cytoprotective effects were examined against 2,2’-azobis(2-methylpropanimidamidine)dihydrochloride(AAPH)-induced oxidative stress in Hep G2 cells.The results showed that these peptides exerted protective effects by suppressing reactive oxygen species(ROS)generation,preventing malondialdehyde(MDA)formation,and upregulating cellular antioxidant enzyme activities(SOD,CAT,and GSH-Px)in a dose-dependent manner.Further experiments proved that these peptides exerted antioxidant effects via Nrf2/ARE-mediated signaling pathway by promoting Nrf2 nuclear translocation,inhibiting ubiquitination,and enhancing transcription capacity of Nrf2 in Hep G2 cells.These findings provide the molecular basis for the effects of antioxidant peptides derived from Chinese baijiu,which is important for a deeper understanding of the relationship between human health and moderate drinking.

Developing high-efficiency base editors by combining optimized synergistic core components with new types of nuclear localization signal peptide

The clustered regularly interspaced short palindromic repeats(CRISPR)–CRISPR-associated protein(Cas) system has been widely used for genome editing. In this system, the cytosine base editor(CBE) and adenine base editor(ABE) allow generating precise and irreversible base mutations in a programmable manner and have been used in many different types of cells and organisms. However, their applications are limited by low editing efficiency at certain genomic target sites or at specific target cytosine(C) or adenine(A) residues. Using a strategy of combining optimized synergistic core components, we developed a new multiplex super-assembled ABE(sABE) in rice that showed higher base-editing efficiency than previously developed ABEs. We also designed a new type of nuclear localization signal(NLS) comprising a FLAG epitope tag with four copies of a codon-optimized NLS(F4NLS^(r2)) to generate another ABE named F4NLS-sABE. This new NLS increased editing efficiency or edited additional A at several target sites. A new multiplex super-assembled CBE(sCBE) and F4NLS^(r2) involved F4NLS-sCBE were also created using the same strategy. F4NLS-sCBE was proven to be much more efficient than sCBE in rice. These optimized base editors will serve as powerful genome-editing tools for basic research or molecular breeding in rice and will provide a reference for the development of superior editing tools for other plants or animals.

Endogenous Endothelin-1 Regulates Hypoxia-Induced Atrial Natriuretic Peptide Secretion by Activating the MAPK/ERK and PI3K/Akt Signaling Pathways in Isolated Beating Rabbit Atria

The present study investigated a possible mechanism for endogenous endothelin-1 (ET-1) regulation of atrial natriuretic peptide (ANP) secretion in isolated perfused acute hypoxic rabbit atria. Acute hypoxia significantly enhanced the release of ET-1 and the expression of the ET receptor (ETR) type A and B (ETRA and ETRB) in atrial tissues, with a concomitant increase in ANP secretion. The ETRA or ETRB antagonist, BQ123 (0.3 μmol/L) or BQ788 (0.3 μmol/L), respectively attenuated hypoxia-induced ANP secretion. Both antagonists significantly attenuated the levels of hypoxiainduced atrial phosphorylated (p)-extracellular signal-regulated kinase (ERK) and p-protein kinase B (Akt). The ERK and Akt inhibitors, PD098059 (30 μmol/L) and LY294002 (30 μmol/L), respectively mimicked the effect of the ETR antagonists. These results demonstrated that acute hypoxia- mediated atrial ET-1 regulated ANP secretion through ETR and the subsequent mitogenactivated protein kinase (MAPK)/ERK and ETR-phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathways. These pathways may mediate atrial endocrine functions under hypoxic conditions.

Improved extracellular endo-1,4-β-mannosidase activity of recombinant Pichia pastoris by optimizing signal peptide

In order to improve the extracellular endo-1,4-β-mannosidase(MAN) activity of recombinant Pichia pastoris, optimization of signal peptides was investigated. At first, five potential signal peptides(W1, MF4 I, INU1 A, αpre, HFBI) were chosen to be analyzed by Signal P 4.0, among which W1 was designed. Then, the widely used signal peptide α-factor in expression vector p GAPZαA was replaced by those five signal peptides to reconstruct five new expression vectors. MAN activity was assayed after expression vectors were transformed into Pichia pastoris. The data show that the relative efficiencies of W1, MF4 I, INU1 A, αpre, and HFBI signal peptides are 23.5%, 203.5%, 0, 79.7%, and 120.3% compared with α-factor, respectively. The further gene copy number determination by the quantitative real-time PCR reveals that the MAN activities mediated by α-factor from 1 to 6 gene copy number levels are 12.95, 43.33, 126.63, 173.53, 103.23 and 88.63 U/m L, while those mediated by MF4 I are 79.22, 133.89, 260.14, 347.5, 206.15 and 181.89 U/m L, respectively. The maximum MAN activity reached 347.5 U/m L with 4 gene copies mediated by MF4 I. These results indicate that replacing the signal peptide α-factor with MF4 I and increasing MAN gene copies to a proper number can greatly improve the secretory expression of MAN.

Signal Peptide and Denaturing Temperature are Critical Factors for Efficient Mammalian Expression and Immunoblotting of Cannabinoid Receptors

Many researchers employed mammalian expression system to artificially express cannabinoid receptors, but immunoblot data that directly prove efficient protein expression can hardly be seen in related research reports. In present study, we demonstrated cannabinoid receptor protein was not able to be properly expressed with routine mammalian expression system. This inefficient expression was rescued by endowing an exogenous signal peptide ahead of cannabinoid receptor peptide. In addition, the artificially synthesized cannabinoid receptor was found to aggregate under routine sample denaturing temperatures (i.e.,≥95°C), forming a large molecular weight band when analyzed by immuno-blotting. Only denaturing temperatures ≤75°C yielded a clear band at the predicted molecular weight. Collectively, we showed that efficient mammalian expression of cannabinoid receptors need a signal peptide sequence, and described the requirement for a low sample denaturing temperature in immuno-blot analysis. These findings provide very useful information for efficient mammalian expression and immuno-blotting of membrane receptors.

无脊椎动物胰岛素样蛋白(Insulin-like/related peptides)研究进展——以昆虫为例

胰岛素样蛋白(Insulin-like/related peptides,ILPs)是无脊椎动物中胰岛素的同源基因。以昆虫为例,概述了ILPs的结构、表达以及相关通路特别是胰岛素信号通路(Insulin signaling pathway),并总结了其在调控机体生长、发育、新陈代谢、繁殖和免疫等生命过程中的作用。

Isolation and characterization of novel peptides from fermented products of Lactobacillus for ulcerative colitis prevention and treatment

Ulcerative colitis(UC)is an incurable and highly complex digestive disease affecting millions of people worldwide.Compared to the current therapeutic drugs,bioactive peptides are more promising and safe substances as functional foods or drugs for the prevention and treatment of UC.The alcohol-soluble components from fermentation broth by fresh wheat germ and apple(AC-WGAF)were found to be effective in UC prevention in dextran sulfate sodium-induced mice in vivo.Herein,4 novel peptides are identifi ed from AC-WGAF by membrane ultrafi ltration,recycling preparative high-performance liquid chromatography,and matrix-assisted laser desorption–ionization time-of-fl ight/time-of-fl ight mass spectrometry,possessing anticolitis activity via using an in vitro model.One of those peptides named T24(PVLGPVRGPFPLL)exhibited the most remarkable anti-colitis activity by preventing tight junction protein loss,maintaining epithelial barrier integrity,and promoting cell proliferation during in vitro and in vivo studies by regulating mitogen-activated protein kinase signaling pathways.Thus,T24 is a promising peptide as a functional food or novel drug for UC prevention and treatment.

血清SCUBE1、Lp-PLA2水平与急性STEMI患者冠状动脉高血栓负荷的关系

目的探讨血清可溶性信号肽-CUB-表皮生长因子样结构域蛋白1(SCUBE1)、脂蛋白磷脂酶A2(Lp-PLA2)与急性ST段抬高型心肌梗死(STEMI)患者冠状动脉高血栓负荷(HTB)的关系。方法选取126例急性STEMI患者(急性STEMI组),根据血栓分级分为HTB患者57例和非HTB患者69例;另选取87名健康体检者为对照组。用酶联免疫吸附法检测血清SCUBE1、Lp-PLA2;用多因素Logistic回归分析急性STEMI患者冠状动脉HTB的影响因素;用受试者工作特征(ROC)曲线评估血清SCUBE1、Lp-PLA2水平对急性STEMI患者冠状动脉HTB的预测价值。结果急性STEMI组血清SCUBE1、Lp-PLA2水平高于对照组(P均<0.05)。HTB患者年龄、吸烟比例、低密度脂蛋白胆固醇、白细胞计数、SCUBE1、Lp-PLA2水平高于非HTB患者(P均<0.05),两者性别、基础疾病、罪犯血管、Gensini评分、左室射血分数比较差异无统计学意义(P均>0.05)。多因素Logistic回归分析显示,年龄增加、吸烟和血清SCUBE1、Lp-PLA2水平升高为急性STEMI患者冠状动脉HTB的独立危险因素(P均<0.05)。ROC曲线分析显示,血清SCUBE1、Lp-PLA2水平联合预测急性STEMI患者冠状动脉HTB的曲线下面积为0.874,大于二者单独预测的0.794、0.791(P均<0.05)。结论急性STEMI患者血清SCUBE1、Lp-PLA2水平升高与冠状动脉HTB密切相关,二者联合检测对急性STEMI患者冠状动脉HTB的预测价值较高。

血清UⅡ和SCUBE1对阻塞性睡眠呼吸暂停低通气综合征患者心血管事件结局的预测价值

目的研究血清尾加压素Ⅱ(urotensinⅡ,UⅡ)和信号肽-CUB-表皮生长因子样结构域蛋白1(signal peptide,CUB domain and EGF like domain containing 1,SCUBE1)对阻塞性睡眠呼吸暂停低通气综合征(obstructive sleep apnea-hypopnea syndrome,OSAHS)患者主要不良心血管事件(major adverse cardiovascular events,MACE)发生的预测价值。方法选取2019-02/2022-02月作者医院诊治的106例OSAHS患者(OSAHS组)和同期体检的60例健康人(对照组)为研究对象。根据睡眠呼吸暂停低通气指数(apnea hypopnea index,AHI)和夜间最低氧饱和度(lowest oxygen saturation,LSaO_(2)),分为轻度组(n=42)、中度组(n=36)和重度组(n=28)。根据随访1年期间是否发生MACE,分为MACE组(n=32)和非MACE组(n=74)。采用酶联免疫吸附试验(enzyme linked immunosorbent assay,ELISA)检测血清UⅡ、SCUBE1水平。采用Logistic回归分析和受试者工作特征(receiver operating characteristic,ROC)曲线分析血清UⅡ、SCUBE1水平对OSAHS患者MACE发生的预测价值。结果OSAHS组患者血清UⅡ、SCUBE1水平均明显高于对照组,组间比较差异具有统计学意义(P均<0.001)。轻度组、中度组及重度组OSAHS患者血清UⅡ、SCUBE1水平依次升高,组间比较差异均具有统计学意义(P均<0.05)。MACE组OSAHS患者OSAHS病程、AHI、血清UⅡ水平、SCUBE1水平均明显高于非MACE组,LSaO_(2)水平低于非MACE组,组间比较差异均具有统计学意义(P均<0.05)。AHI、血清UⅡ、血清SCUBE1是影响OSAHS患者MACE发生的独立危险因素,LSaO_(2)是保护因素。血清UⅡ、SCUBE1及二者联合对预测OSAHS患者MACE发生的曲线下面积(area under the curve,AUC)分别为0.846(95%CI:0.801~0.894),0.812(95%CI:0.770~0.839),0.904(95%Cl:0.860~0.943),二者联合检测的预测效能高于血清UⅡ、SCUBE1单独检测。结论OSAHS患者血清UⅡ、SCUBE1水平升高,二者与OSAHS病情程度有关,均参与OSAHS疾病进展过程。血清UⅡ、SCUBE1联合检测对OSAHS患者MACE发生具有较高的预测价值,是新的评估MACE预后的血清标志物。

多个稻曲病菌效应因子的信号肽验证和表达分析

【目的】信号肽对效应因子的分泌至关重要,影响病原微生物的致病进程。前期鉴定到在稻曲病菌侵染水稻花器官过程中显著上调表达的10个效应因子基因,但这些效应因子是否含有功能性信号肽及其表达模式尚不明确。【方法】利用SignaIP-5.0数据库预测、烟草瞬时表达系统和酵母信号肽分泌实验,分析并鉴定这些效应因子的信号肽。利用实时荧光定量PCR技术,检测效应因子基因的表达模式。【结果】UV_44、UV_1548、UV_1567等10个稻曲病菌效应因子均含有信号肽。烟草瞬时表达结果显示,含有信号肽的eYFP融合蛋白在细胞质壁分离后均能分泌到质外体空间。酵母菌信号肽分泌结果显示,分别携带这10个信号肽的酵母菌株可在以棉子糖为唯一碳源的培养基上生长,且与TTC发生显色反应。实时荧光定量结果表明,除了UV_6754,其余9个效应因子基因的表达模式不尽相同,其中UV_44、UV_1567、UV_3667、UV_4213、UV_4989、UV_5215和UV_8184的表达量在接种后显著升高。【结论】这10个稻曲病菌效应因子均含有分泌功能的信号肽,编码效应因子的基因在稻曲病菌侵染过程中具有不同的表达模式。该结果为深入研究以上稻曲病菌效应因子的功能奠定了基础。

多囊卵巢综合征患者卵巢颗粒细胞胰岛素抵抗的相关信号通路

胰岛素抵抗(insulin resistance,IR)与多囊卵巢综合征(polycystic ovary syndrome,PCOS)的发生发展有关,而与IR相关的胰岛素信号通路异常会引起卵巢局部代谢紊乱,进而影响卵泡发育及卵子质量。PCOS卵巢颗粒细胞中胰岛素作用的经典通路,包括磷脂酰肌醇3激酶(phosphoinositide 3-kinase,PI3K)/蛋白激酶B(protein kinase B,Akt)通路和丝裂原激活的蛋白激酶(mitogen-activated protein kinase,MAPK)/细胞外信号调节激酶(extracellular signal-regulated kinase,ERK)通路;与炎症相关的通路包括Toll样受体(Toll-like receptor,TLR)/核因子κB(nuclear factor-κB,NF-κB)通路等;氧化应激相关通路包括核转录因子红系2相关因子2(nuclear factor-erythroid 2-related factor 2,Nrf2)/血红素加氧酶-1(heme oxygenase-1,HO-1)途径和GTP酶免疫相关蛋白7(GTPase of immunity-associated protein 7,GIMAP7)/音猬因子(sonic hedgehog,SHH)途径;与脂质代谢相关的通路如激活转录因子4(activating transcription factor 4,ATF4)通路等。明确PCOS患者卵巢颗粒细胞中IR相关信号转导通路,增进PCOS病理生理机制的认识,进一步为PCOS的治疗提供新思路。

小麦肽通过抑制炎症和PI3K/mTOR通路改善乙醇诱导胃黏膜损伤

该研究的目的是探究小麦肽对乙醇造成的胃黏膜损伤的保护作用及其机制。使用小麦肽进行处理后,乙醇诱导小鼠胃黏膜损伤模型和人胃黏膜上皮细胞(human gastric mucosal epithelial cell,GES-1)细胞损伤模型,观察小鼠体重变化和胃组织损伤状况,评估氧化应激、炎症和自噬相关蛋白表达水平。小麦肽预处理显著改善了乙醇诱导的小鼠体重降低,提高了胃组织和GES-1细胞内抗氧化酶活力和一氧化氮(NO)含量,减少脂质过氧化发生。病理组织切片显示,小麦肽预处理后,胃组织损伤显著减少。此外,小麦肽降低了组织内促炎因子表达,并通过抑制GES-1细胞中PI3K/AKT/mTOR通路激活,提高了LC3-Ⅱ蛋白表达。小麦肽可以通过调节抗氧化能力和促炎因子表达,抑制PI3K/mTOR通路激活等方式,改善乙醇诱导的胃黏膜损伤。

毕赤酵母外源蛋白分泌及折叠途径的改良进展

工业、农业和医药等领域常用的活性蛋白和工业酶大多数通过异源表达系统获得。毕赤酵母(Pichia pastoris)是优秀的外源蛋白表达宿主之一,以毕赤酵母为宿主的表达系统具有遗传稳定性好、翻译后修饰、蛋白表达和分泌水平高及生产成本低等优点,但在高效表达过程中外源蛋白过量聚集会导致目标蛋白不能正确折叠和有效分泌,从而影响蛋白表达水平。概述了通过信号肽优化、分子伴侣优化以及融合蛋白表达等分泌及折叠途径的改良,从而促进外源蛋白高效表达的研究进展。

NLS-KALA-SA纳米粒的制备及细胞核靶向性评价

目的构建由融合肽KALA、硬脂酸(SA)、核定位信号(NLS)组成的细胞核靶向多肽纳米载体(NLSKALA-SA,NKSN)。方法采用Fmoc多肽固相合成法人工合成NLS-KALA-SA多肽纳米载体。结果NLSKALA-SA纳米颗粒呈球形,平均尺寸为(76.4±7.6)mm,Zeta电位为(43.7±5.8)mV。纳米颗粒呈正态分布,粒径分布较窄,多分散度指数(PI<0.3)。细胞摄取实验研究表明,包载香豆素-6(C-6)的NLS-KALA-SA纳米粒子(C-6/NKSN)主要积聚在A549细胞的细胞核中。细胞毒性实验研究表明,在检测浓度为0.01~1000 mg/mL时,NLS-KALA-SA对A549细胞几乎没有细胞毒性。结论NLS-KALA-SA是一种安全无毒且具有跨膜转运和核定位功能的纳米载体,有望成为一种有前景的癌症治疗多肽纳米载体。