A ratiometric fluorescent sensor for the detection of phosphate

Over the past few years, ratiometric fluorescent nanoprobes have garnered substantial interest because of their self-calibration characteristics. This research developed a ratiometric fluorescent sensor to detect phosphate. Through encapsulating luminescent materials, gold nanoclusters (AuNCs) and carbon dots (CDs) into a zeolitic imidazolate framework-8 (ZIF-8), the fluorescence signal of AuNCs was enhanced, while that of CDs was suppressed. After phosphate was added, it could decompose ZIF-8, and AuNCs and CDs were released, which weakened the fluorescence signal of the AuNCs while restoring that of the CDs. Thereby, this makes CDs/AuNCs@ZIF-8 a potential fluorescent sensor for phosphate determination. The ratiometric sensor had facile synthesis, good selectivity, and a low detection limit. Therefore, this sensor was an effective tool for the detection of phosphate.     

慕课在生物化学课程教学中的作用——华南农业大学《生物化学》“MOOC+线上见面课”课程教学实践

生物化学不仅是生物类专业的基础课,也是发展最快的前沿课程之一。传统的线下教学模式面对生物化学的繁杂体系暴露出许多问题,通常教学效果不佳。随着互联网技术的发展,“互联网+”教育得到快速发展。慕课与微课等线上课程为许多高校提供了丰富的学习资源,钉钉课堂、腾迅课堂、雨课堂、微信交流平台等线上课程直播,也让学生足不出户就能实现同步学习。线上教学在新冠疫情期间成为全国大中小学院校的主要教学模式,但经过几年的推广,单纯的线上教学在教学效果方面也暴露出诸多问题。为充分发挥线上、线下教学的各自优势,混合式教学成为发展方向。华南农业大学在2019年初开始与智慧树平台合作,建立生物化学的教学慕课,在2020年新冠疫情期间,我校生物化学课程教学采用了“MOOC+线上见面课”的线上混合教学模式。教学反馈结果显示,学生单纯依靠MOOC并不能很好地完成生物化学的学习,但“MOOC+线上见面课”则获得了学生的普遍认可。该教学模式不仅能提高学生的学习兴趣和学习主动性,在一定程度上也能提升教学质量和学习效果,为今后 “MOOC+线下课”的应用提供了参考。     

Visualization photofragmentation‐induced rhodamine B release from gold nanorod delivery system by combination two‐photon luminescence imaging with correlation spectroscopy

Plasmon‐enhanced gold nanorod (AuNR) with high photothermal conversion efficiency is a promising light‐controllable nanodrug delivery system for cancer therapy. Understanding the mechanism for the light‐controllable drug release of AuNR delivery systems is important for the development of nanomedicine. In this study, the rhodamine B (RB) released from AuNR‐RB nanodelivery system was quantitated and visualized by using two‐photon luminescence (TPL) imaging combined with correlation spectroscopy. The photofragmentation of AuNR induced by femtosecond pulsed laser was revealed by TPL correlation spectroscopy when the laser energy was above the thermal damage threshold of AuNR, and the RB released from this nanodrug delivery system was visualized by TPL imaging. Furthermore, the photofragmentation‐induced release of RB from AuNR‐RB nanodelivery system was visualized in living MCF‐7 breast cancer cells by TPL imaging combined with correlation spectroscopy. These results provided a novel optical approach to quantify the release of drugs from gold nanocarriers in complex biological media.     

一流课程“微生物学模块化实验”的建设与实践

我校“微生物学模块化实验”课程获评为首批国家级线上一流课程。建设优秀教学团队、优良线下课程、创新课堂教学和加强课程思政建设是一流课程建设的4个核心要素。首先，我们通过开教学研讨会集体备课；组建微信群及时交流讨论；组织申报教改项目、撰写教改论文、编写教材、参加教学比赛等活动，建设一支教学水平高、教改愿望强、分工协作好的教学团队。其次，按“金课”标准建设线下课程体系，采用以模块化形式将微生物学实验建设成综合性、研究型实验课程，形成了“学习内容模块化、学习方式探究性、实验技术综合性”的特色；线上课程增加拓展性学习内容，提升课程的广度和深度。三是加强课程思政建设，将家国情怀、科学家精神、学术规范、社会责任意识等课程思政元素无痕化融入课程建设中。在课堂教学中，综合运用案例教学法、探究性教学法和以赛代练教学法促进学生掌握实验技术，提高分析问题的能力，形成良好的科学素养。     

Bacterial Oxidation of Refractory Sulfide Ores for Gold Recovery

Abstract

The microbiological leaching of refractory sulfide ores (pyrite, arsenopyrite) for recovery of gold is reviewed in this article. The underlying physiological, biochemical, and genetic fundamentals of the bacteria involved (Thiobacillus and Sulfolobus spp.) are complex and have yet to be elucidated in depth. The chemistry of acid and biological leaching of pyrite and arsenopyrite minerals is also complex, and many of the individual reactions are not known in detail. Bacterial leaching is discussed in relation to chemical speciation at acid pH values. Attempts to develop models for a better understanding of bioleaching processes are summarized. The importance of pH, redox potential, temperature, sulfur balance, and toxic metals is evaluated for optimizing conditions for bacterial activity. Gold is finely disseminated in refractory sulfide ores, thereby decreasing Au recoveries upon conventional cyanidation for gold dissolution. In the bioleaching process, bacteria remove the sulfide minerals by oxidative dissolution and thus expose Au to extraction with cyanide solution. Stirred tank reactors appear most suited for this biological leaching process. The overall oxidation of the sulfides is an important variable for gold recovery. Pilot- and commercial-scale bioleaching processes for gold-containing pyrite and arsenopyrite ores are reviewed. This application of mineral biotechnology competes favorably with pressure leaching and roasting processes, both of which are problematic and energy-intensive alternatives for pretreatment of auriferous pyrite/arsenopyrite ores.     

Electrochemistry of cytochromes P450: Analysis of current-voltage characteristics of electrodes with immobilized cytochromes P450 for the screening of substrates and inhibitors

In the current study, an approach to elucidating the substrate specificity of cytochromes P450 based on the analysis of current-voltage characteristics of voltammograms and amperograms is proposed. Data on the electrochemical behavior of bioelectrodes with immobilized cytochromes P450 2B4, 1A2, 3A4, 11A1 (P450scc), and 51b1 (Mycobacterium tuberculosis sterol 14α-demethylase or CYP51 MT) in the presence of typical substrates and inhibitors for these hemoprotein forms are reported. Immobilization of the enzymes was accomplished by using graphite screen-printed electrodes modified with gold nanoparticles and with the synthetic membrane-like compound didodecyldimethylammonium bromide. The method of electro-analysis can be applied to the search of potential substrates and inhibitors of cytochromes P450 and to creation of multichannel electrochemical plates (chips, panels) with immobilized cytochromes P450. Published in Russian in Biokhimiya, 2009, Vol. 74, No. 4, pp. 542–549.     

New Silver-Gold Intensification Method of Diaminobenzidine for Double-Labeling Immunoelectron Microscopy

The available methods for double-labeling preembedding immunoelectron microscopy are highly limited because not only should the ultrastructure be preserved, but also the different antigens should be visualized by reaction end products that can be clearly distinguished in gray-scale images. In these procedures, one antigen is detected with 3,3′-diaminobenzidine (DAB) chromogen, resulting in a homogeneous deposit, whereas the other is labeled with either a gold-tagged immunoreagent, or DAB polymer, on the surface of which metallic silver is precipitated. The detection of the second antigen is usually impeded by the first, leading to false-negative results. The authors aimed to diminish this hindrance by a new silver intensification technique of DAB polymer, which converts the deposit from amorphous to granular. The method includes three major postdevelopmental steps: (1) treatment of nickel-enhanced DAB with sulfide, (2) silver deposition in the presence of hydroquinone under acidic conditions, and (3) precious metal replacement with gold thiocyanate. This new sulfide-silver-gold intensification of DAB (SSGI) allows a subsequent detection of other antigens using DAB. In conclusion, the new technique loads fine gold particles onto the DAB deposit at a very low background level, thereby allowing a reliable discernment between the elements stained for the two antigens at the ultrastructural level.     

Highlighting the roles of transition metals and speciation in chemical biology

Transition metal ions play key structural and functional roles, affecting structures of biomolecules and enzyme function. The importance of transition metal ions in chemical biology is, thus, undisputed. However, the aqueous chemistry of metal ions is complicated because they form species in several protonation and redox states. In the presence of metabolites, metal ions can also form coordination complexes. The existence of several species is relevant because enzymes and membrane receptors can distinguish between species even when they are rapidly equilibrating. Thus, metal ions, enzyme cofactors, and therapeutic agents are sensitive to the metal ion speciation chemistry because it affects their interaction with enzymes and other biomolecules. Speciation is also crucial for metal-containing bioorthogonal reactions, since water and metabolites stabilize active catalysts, affect chemoselectivity and reaction yields.