A Nisin Bioassay Based on Bioluminescence

A Lactococcus lactis subsp. lactis strain that can sense the bacteriocin nisin and transduce the signal into bioluminescence was constructed. By using this strain, a bioassay based on bioluminescence was developed for quantification of nisin, for detection of nisin in milk, and for identification of nisin-producing strains. As little as 0.0125 ng of nisin per ml was detected within 3 h by this bioluminescence assay. This detection limit was lower than in previously described methods.     

甲醇固定导致绿色荧光蛋白的荧光消失

发现用甲醇固定转染了绿色荧光蛋白(GFP)基因的细胞会导致GFP的荧光消失,而当用聚甲醛固定时,GFP的荧光就没有失去。因此建议避免用甲醇对有GFP表达的细胞进行免疫组化前的固定。     

Green Fluorescent Protein with Anionic Tryptophan-Based Chromophore and Long Fluorescence Lifetime

Spectral diversity of fluorescent proteins, crucial for multiparameter imaging, is based mainly on chemical diversity of their chromophores. Recently we have reported, to our knowledge, a new green fluorescent protein WasCFP—the first fluorescent protein with a tryptophan-based chromophore in the anionic state. However, only a small portion of WasCFP molecules exists in the anionic state at physiological conditions. In this study we report on an improved variant of WasCFP, named NowGFP, with the anionic form dominating at 37°C and neutral pH. It is 30% brighter than enhanced green fluorescent protein (EGFP) and exhibits a fluorescence lifetime of 5.1 ns. We demonstrated that signals of NowGFP and EGFP can be clearly distinguished by fluorescence lifetime in various models, including mammalian cells, mouse tumor xenograft, and Drosophila larvae. NowGFP thus provides an additional channel for multiparameter fluorescence lifetime imaging microscopy of green fluorescent proteins.     

Fluorescent Protein Based FRET Pairs with Improved Dynamic Range for Fluorescence Lifetime Measurements

Fluorescence Resonance Energy Transfer (FRET) using fluorescent protein variants is widely used to study biochemical processes in living cells. FRET detection by fluorescence lifetime measurements is the most direct and robust method to measure FRET. The traditional cyan-yellow fluorescent protein based FRET pairs are getting replaced by green-red fluorescent protein variants. The green-red pair enables excitation at a longer wavelength which reduces cellular autofluorescence and phototoxicity while monitoring FRET. Despite the advances in FRET based sensors, the low FRET efficiency and dynamic range still complicates their use in cell biology and high throughput screening. In this paper, we utilized the higher lifetime of NowGFP and screened red fluorescent protein variants to develop FRET pairs with high dynamic range and FRET efficiency. The FRET variations were analyzed by proteolytic activity and detected by steady-state and time-resolved measurements. Based on the results, NowGFP-tdTomato and NowGFP-mRuby2 have shown high potentials as FRET pairs with large fluorescence lifetime dynamic range. The in vitro measurements revealed that the NowGFP-tdTomato has the highest Förster radius for any fluorescent protein based FRET pairs yet used in biological studies. The developed FRET pairs will be useful for designing FRET based sensors and studies employing Fluorescence Lifetime Imaging Microscopy (FLIM).     

Variants of Green Fluorescent Protein GFPxm

As research progresses, fluorescent proteins useful for optical marking will evolve toward brighter, monomeric forms that are more diverse in color. We previously reported a new fluorescent protein from Aequorea macrodactyla, GFPxm, that exhibited many characteristics similar to wild-type green fluorescent protein (GFP). However, the application of GFPxm was limited because GFPxm expressed and produced fluorescence only at low temperatures. To improve the fluorescent properties of GFPxm, 12 variants were produced by site-directed mutagenesis and DNA shuffling. Seven of these mutants could produce strong fluorescence when expressed at 37°C. The relative fluorescence intensities of mutants GFPxm16, GFPxm18, and GFPxm19 were higher than that of EGFP (enhanced GFP) when the expression temperature was between 25 and 37°C, and mutants GFPxm16 and GFPxm163 could maintain a high fluorescence intensity even when expressed at 42°C. Meanwhile, at least 4 mutants could be successfully expressed in mammalian cell lines. The fluorescence spectra of 6 of the 12 mutants had a progressive red shift. The longest excitation-emission maximum was at 514/525 nm. In addition, 3 of the 12 mutants had two excitation peaks including an UV-excitation peak, while another mutant had only one UV-excitation peak.     

Use of Green Fluorescent Protein in mouse embryos

Green Fluorescent Protein (GFP) has rapidly been established as a versatile and powerful cell marker in many organisms. Initial problems in using it in mammalian cells were solved by introducing mutations to increase its solubility at higher temperatures, such that GFP has now been used as a reporter in both gene expression and cell lineage studies, and to localize proteins within mammalian cells. GFP has two unique advantages: (i) the protein becomes fluorescent in an autocatalytic reaction, so that it can be introduced into any cell type simply as a cDNA or mRNA, or as protein; (ii) it is "bright" enough to be visualized in living cells under conditions that do not cause photodamage to the cells. In this article we outline the ways in which we have used GFP mRNA and cDNA in our studies of mouse cell lineages, and to characterize the behavior of proteins within the embryos.     

绿色荧光蛋白在转基因研究中的应用

绿色荧光蛋白(green fluorescent prote in,GFP)是一种能够自身催化形成生色团并在蓝光或紫外光激发下发出绿色荧光的蛋白。有现代生物学北斗星之美誉的它,在生物学的很多领域都有广泛应用。GFP具有荧光稳定、易于检测、表达调控简单、生物安全性好等优点,在转基因研究中的各个方面均应用颇多。就GFP在转基因研究中的应用特点及应用进展做一综述。     

Green Fluorescent Protein Purification by Organic Extraction

Green fluorescent protein (GFP) is widely used as an excellent reporter molecule in biochemistry and cell biology. Some biochemical and immunological assays require high-purity GFP. However, the majority of current procedures for GFP purification include multiple time-consuming chromatography steps with a low yield of the desired product or require tag-containing proteins. An alternative method is described for the GFP purification without affinity extensions using organic extraction yielding a highly homogeneous protein indistinguishable in spectroscopic properties from that purified by previous methods.     

A Photostable Green Fluorescent Protein Variant for Analysis of Protein Localization in Candida albicans

Fusions to the green fluorescent protein (GFP) are an effective way to monitor protein localization. However, altered codon usage in Candida species has delayed implementation of new variants. Examination of three new GFP variants in Candida albicans showed that one has higher signal intensity and increased resistance to photobleaching.The human fungal pathogen Candida albicans can cause severe infections, particularly in immunocompromised patients. Important insights into its pathogenesis have been obtained by analyzing fusions to green fluorescent protein (GFP) (8). Although GFP tagging has been very successful, many fusion proteins are not easily detected. New GFP variants with improved fluorescence and protein folding properties have been identified by genetic approaches in other organisms (2, 7, 8). However, these GFP variants have not been assessed in C. albicans and related species, presumably because of the added difficulties of attempting heterologous expression in C. albicans.To adapt GFP for effective use in C. albicans, Cormack et al. introduced three types of codon changes: the S65G S72A mutations to enhance fluorescence; the CTG codon 201 change to TTG, since CUG is translated as Ser instead of Leu in C. albicans; and the optimization of the other codons for translation in C. albicans (1). This variant, known as YeGFP3, was introduced into convenient vectors for creating gene fusions in C. albicans (4). Another version of eGFP known as mut2 (S65A V68L S72A Q80R) was adapted for C. albicans by changing the CTG codon but without further codon optimization (5). These obstacles to heterologous expression in C. albicans have presumably delayed implementation of newer versions of GFP. Therefore, in this study three different GFP variants were introduced into YeGFP3 and examined for function in C. albicans.The GFP variants were constructed using standard methods to introduce changes in the coding sequence of YeGFP3. In brief, mutagenic oligonucleotides were used to prime PCR synthesis of a plasmid carrying YeGFP3, the template DNA was then destroyed by digestion with DpnI, and then the resulting DNA was transformed into Escherichia coli. DNA sequencing (carried out by the Stony Brook University DNA Sequencing Facility) confirmed that the correct substitutions were present. The mutant GFP genes were then released as PstI-AscI fragments and then were subcloned to replace the corresponding GFP fragment of plasmid pFa-GFP-URA3 (6), which carries a PCR cassette module for creating GFP fusions in C. albicans. Because of the large number of changes, the mutants were given the more convenient names of CaGFPα (F64L S65T F99S M153T V163A), CaGFPβ (F64L S65T N149K M153T I167T; also known as emerald), and CaGFPγ (F64L S65C V163A I167T). The CaGFPγ was also introduced into vectors that contain selectable markers HIS1 and ARG4 (6). DNA sequences used to design primers for creating GFP fusions in C. albicans were as follows: forward primer, 5′ (region of homology)-GGTGCTGGCGCAGGTGCTTC-3′, and reverse primer, 5′ (region of homology)-TCTGATATCATCGATGAATTCGAG-3′.CDC11-GFP fusion genes were created in C. albicans by homologous recombination, as described previously (4, 6). In brief, long oligonucleotide primers with homology to the 3′ end of the CDC11 open reading frame were used to prime PCR synthesis of each of the corresponding GFP variant genes plus an adjacent selectable marker gene (URA3). These DNA elements were then introduced into C. albicans cells and allowed to recombine with the homologous region of the CDC11 gene in C. albicans to create the CDC11-GFP fusion genes. Sequences used for the design of PCR primers to amplify the pFa-GFP plasmids are shown above. Cells carrying the indicated CDC11-GFP fusion gene were grown overnight in log phase in synthetic medium (yeast nitrogen base plus amino acids and dextrose). Cdc11-GFP fluorescence intensity was analyzed with an Olympus BH2 microscope equipped with a Zeiss AxioCam camera run by Openlab software. The relative GFP signal was determined by measuring the intensity of GFP fluorescence of the septin ring and then subtracting the fluorescence of an area immediately adjacent to each ring. All samples were visualized under the same conditions.Samples were prepared for Western blot analysis by resuspending cells in TNE lysis buffer (10 mM Tris base, 1 mM EDTA, 100 mM NaCl) with 100× protease mix (40 mg/ml pepstatin A, 40 mg/ml aprotinin, 20 mg/ml leupeptin) and then agitating in the presence of glass beads. The supernatant was collected after low-speed centrifugation at 3,000 rpm for 1 min, protein concentrations were determined by the bicinchoninic acid (BCA) protein assay (Pierce), and then equal amounts of protein extract were separated by gel electrophoresis and transferred to a Protran nitrocellulose membrane (Whatman GmbH). The blots were incubated with mouse anti-GFP (Millipore), rabbit anti-glucose-6-phosphate dehydrogenase (anti-G6PD; Sigma), or rabbit anti-Cdc11 (Santa Cruz Biotechnology) primary antibodies; washed; and then incubated with either goat anti-mouse IRDye 800cw or goat anti-rabbit IRDye 680 (Li-Cor Biosciences, Lincoln, NE). The immunoreactive proteins were visualized with a Li-Cor fluorescence scanner run by Odyssey software.Three new GFP variants based on YeGFP3 were constructed by introducing mutations predicted to improve either the fluorescence properties or protein folding (2, 7, 8). Because multiple changes were introduced into each variant, they were given the more convenient names of CaGFPα, CaGFPβ, and CaGFPγ (see above). The key mutations in CaGFPα and CaGFPβ have been described previously (2, 7, 8), but CaGFPγ represents a novel combination of mutations. The 3 new GFP variants plus the YeGFP3 and mut2 versions were compared by fusing them to the C terminus of the Cdc11 septin protein (3). The Cdc11 protein was selected because its restricted localization to the bud neck facilitated microscopic analysis and comparison of fluorescence properties. CDC11-GFP fusion genes were constructed in strain BWP17 (9) using PCR-generated modules with a URA3 selectable marker, as described previously (4, 6).Cells were grown in synthetic medium overnight to log phase at both 30°C and 37°C, temperatures that are commonly used to propagate C. albicans and that may affect the folding properties of GFP. GFP fluorescence was then analyzed by quantifying the intensity of the septin rings in digital images (Fig. ​(Fig.1A).1A). Septin rings were analyzed only if they were obviously in focus and at the same stage of the cell cycle (large budded). CaGFPγ gave a slightly stronger signal than the other variants, which was most obvious at 30°C (Fig. ​(Fig.1A).1A). At least two independent clones were analyzed for each CDC11-GFP variant, and the two gave similar results (data not shown).Open in a separate windowFIG. 1.Properties of Cdc11-GFP fusion proteins. Cells were grown to log phase overnight at the indicated temperature, and then Cdc11-GFP fluorescence was analyzed. (A) Signal intensity for the different versions of Cdc11-GFP was compared in three independent assays in which 50 septin rings per assay were quantified for each different Cdc11-GFP. The average fluorescence intensity was normalized to 100 for Cdc11-YeGPF3. The Cdc11-CaGFPγ variant gave a significantly stronger signal than the other variants (P < 0.001). (B) Western blot analysis comparing the levels of Cdc11-GFP produced in the indicated strains. The lane labeled “neg” refers to the negative-control strain (BWP17) that lacks GFP. Blots were probed with anti-GFP to detect Cdc11-GFP, anti-glucose-6-phosphate dehydrogenase (αG6PD) as a control, and anti-Cdc11 to detect the untagged version of Cdc11.The levels of the Cdc11-GFP proteins at both 30°C and 37°C were compared on two independent Western blots using anti-GFP antibody (Fig. ​(Fig.1B).1B). The relative levels of Cdc11-mut2GFP and Cdc11-CaGFPα were the lowest, consistent with their lower fluorescence intensity. The lower levels of Cdc11-mut2GFP are consistent with the fact that the codons in the mut2 version of GFP were not optimized for expression in C. albicans (5). The Cdc11-YeGFP3 and Cdc11-CaGFPγ were present at higher levels, and the Cdc11-CaGFPβ was produced at even slightly higher levels, consistent with reports that this latter version of GFP (also known as emerald) has improved folding properties (7). The Cdc11-GFP variants did not affect the production of the untagged Cdc11 protein (Fig. ​(Fig.1B1B).Photobleaching is also an important factor for GFP (7), especially in time-lapse studies or Z-stack analysis of different optical sections of cells. Photostability of the GFP variants was examined by taking pictures at 4-s intervals during 1 min of continuous exposure to the fluorescence excitation lamp (Fig. 2A and B). The fluorescence of YeGFP3, mut2GFP, and CaGFPα fused to Cdc11 decayed to 50% of original intensity within 15 to 30 s, and the rate of photobleaching was even higher for CaGFPβ. In contrast, Cdc11-CaGFPγ showed extended photostability at both 30°C and 37°C (half-life [t_1/2] of ∼2 min). Similar results were also obtained for CaGFPγ fused to the Golgi protein Vrg4 (data not shown), although the standard deviations were larger because the mobile Golgi compartments frequently moved out of the focal plane during the time course (data not shown). On a practical level, the Cdc11-GFPγ fluorescence was readily detectable after several minutes of continuous exposure (Fig. ​(Fig.2C),2C), demonstrating its clear advantage for allowing more time to observe protein localization before photobleaching becomes significant.Open in a separate windowFIG. 2.Photostability of GFP variants. (A and B) Relative fluorescence intensity of the GFP variants at 4-s intervals over a time course of 1 min of continuous exposure to the fluorescence excitation lamp after growth at 30°C (A) and at 37°C (B). CaGFPγ showed the best photostability (t_1/2 of ∼2 min). The relative fluorescence was normalized to 100 for each Cdc11-GFP variant at the start of the time course. The results represent the average of three independent assays in which three septin rings were analyzed for each mutant. Error bars indicate standard deviations. (C) Cells carrying Cdc11 fused to YeGFP3 or CaGFPγ were continuously exposed to the fluorescence excitation lamp, and then images of septin rings were captured at the indicated times.Altogether, Cdc11-CaGFPγ had the best overall properties based on protein levels, signal intensity, and photostability in C. albicans. The higher level of Cdc11-CaGFPβ production was apparently offset by increased photobleaching, resulting in no overall advantage for this variant. The Cdc11-CaGFPα was produced at relatively low levels, and it was less photostable compared to the other versions. Thus, CaGFPγ is a novel GFP variant that offers improved features for the study of protein localization in C. albicans and will likely also be useful for expression in other species.     

Oviduct-Specific Enhanced Green Fluorescent Protein Expression in Transgenic Chickens

In this study, we confirmed the ability of the 2-kb promoter fragment of the chicken ovalbumin gene to drive tissue-specific expression of a foreign EGFP gene in chickens. Recombinant lentiviruses containing the EGFP gene were injected into the subgerminal cavity of 539 freshly laid embryos (stage X). Subsequently the embryos were incubated to hatch using phases II and III of the surrogate shell ex vivo culture system. Twenty-four chicks (G0) were hatched and screened for EGFP with PCR. Two chicks were identified as transgenic birds (G1), and these founders were mated with wild-type chickens to generate transgenic progeny. In the generated transgenic hens (G2), EGFP was expressed specifically in the tubular gland of the oviduct. These results show the potential of the chicken ovalbumin promoter for the production of biologically active proteins in egg white.     

Noninvasive Measurement of Bacterial Intracellular pH on a Single-Cell Level with Green Fluorescent Protein and Fluorescence Ratio Imaging Microscopy

We show that a pH-sensitive derivative of the green fluorescent protein, designated ratiometric GFP, can be used to measure intracellular pH (pH_i) in both gram-positive and gram-negative bacterial cells. In cells expressing ratiometric GFP, the excitation ratio (fluorescence intensity at 410 and 430 nm) is correlated to the pH_i, allowing fast and noninvasive determination of pH_i that is ideally suited for direct analysis of individual bacterial cells present in complex environments.     

Photophysical Behavior of mNeonGreen,an Evolutionarily Distant Green Fluorescent Protein

Fluorescent proteins (FPs) feature complex photophysical behavior that must be considered when studying the dynamics of fusion proteins in model systems and live cells. In this work, we characterize mNeonGreen (mNG), a recently introduced FP from the bilaterian Branchiostoma lanceolatum, in comparison to the well-known hydrozoan variants enhanced green fluorescent protein (EGFP) and Aequorea coerulescens GFP by steady-state spectroscopy and fluorescence correlation spectroscopy in solutions of different pH. Blind spectral unmixing of sets of absorption spectra reveals three interconverting electronic states of mNG: a nonfluorescent protonated state, a bright state showing bell-shaped pH dependence, and a similarly bright state dominating at high pH. The gradual population of the acidic form by external protonation is reflected by increased flickering at low pH in fluorescence correlation spectroscopy measurements, albeit with much slower flicker rates and lower amplitudes as compared to Aequorea GFPs. In addition, increased flickering of mNG indicates a second deprotonation step above pH 10 leading to a slight decrease in fluorescence. Thus, mNG is distinguished from Aequorea GFPs by a two-step protonation response with opposite effects that reflects a chemically distinct chromophore environment. Despite the more complex pH dependence, mNG represents a superior FP under a broad range of conditions.     

基于Avi-tag技术的人胚肾细胞内增强型绿色荧光蛋白的生物素化、纯化和检测方法

目的:建立并优化基于Avi-tag标签技术的人胚肾细胞增强型绿色荧光蛋白(eGFP)的定点生物素化标记、纯化和检测方法。方法:分别构建具有Avi-tag标签的eGFP真核表达载体plenti-Avi-eGFP和BirA酶真核过表达载体pQCXIH-BirA,将plenti-Avi-eGFP和pQCXIH-BirA共转染人胚肾293T细胞,12 h后观察Avi-tag标签对eGFP蛋白在细胞内定位的影响;48 h后裂解细胞,用链霉亲和素珠子纯化生物素标记的eGFP,SDS-PAGE观察eGFP纯化和富集情况,并优化基于Western印迹的生物素化eGFP检测方法。结果:Avi-tag标签对eGFP在细胞内的定位无影响,同时BirA酶在293T细胞内可将带Avi-tag标签的eGFP标记上生物素;生物素化的eGFP可特异性地被链霉亲和素珠子纯化和富集,纯度可达95%;Western印迹检测生物素化蛋白的最终条件为5%的BSA作为封闭液和终浓度为100 ng/mL的链霉亲和素-HRP。结论:建立了基于Avi-tag技术的人胚肾细胞内增强型绿色荧光蛋白的生物素化标记、纯化与检测方法,为该方法的广泛应用奠定了前期技术基础。     

Effect of Starvation and the Viable-but-Nonculturable State on Green Fluorescent Protein (GFP) Fluorescence in GFP-Tagged Pseudomonas fluorescens A506

The green fluorescent protein (GFP) gene, gfp, of the jellyfish Aequorea victoria is being used as a reporter system for gene expression and as a marker for tracking prokaryotes and eukaryotes. Cells that have been genetically altered with the gfp gene produce a protein that fluoresces when it is excited by UV light. This unique phenotype allows gfp-tagged cells to be specifically monitored by nondestructive means. In this study we determined whether a gfp-tagged strain of Pseudomonas fluorescens continued to fluoresce under conditions under which the cells were starved, viable but nonculturable (VBNC), or dead. Epifluorescent microscopy, flow cytometry, and spectrofluorometry were used to measure fluorescence intensity in starved, VBNC, and dead or dying cells. Results obtained by using flow cytometry indicated that microcosms containing VBNC cells, which were obtained by incubation under stress conditions (starvation at 37.5°C), fluoresced at an intensity that was at least 80% of the intensity of nonstressed cultures. Similarly, microcosms containing starved cells incubated at 5 and 30°C had fluorescence intensities that were 90 to 110% of the intensity of nonstressed cells. VBNC cells remained fluorescent during the entire 6-month incubation period. In addition, cells starved at 5 or 30°C remained fluorescent for at least 11 months. Treatment of the cells with UV light or incubation at 39 or 50°C resulted in a loss of GFP from the cells. There was a strong correlation between cell death and leakage of GFP from the cells, although the extent of leakage varied depending on the treatment. Most dead cells were not GFP fluorescent, but a small proportion of the dead cells retained some GFP at a lower concentration than the concentration in live cells. Our results suggest that gfp-tagged cells remain fluorescent following starvation and entry into the VBNC state but that fluorescence is lost when the cells die, presumably because membrane integrity is lost.     

板栗疫病菌绿色荧光与红色荧光蛋白共定位载体的构建

低毒病毒-板栗疫病菌组合是研究病毒与宿主相互作用的一个优秀的模式系统.我们构建了含绿色荧光蛋白基因gfp的载体pCPXHY2GFP与含红色荧光蛋白基因rfp的载体pCPXG418RFP,并用于转化野生型菌株EP155,获得了以潮霉素为筛选标记、表达绿色荧光蛋白的转化株pCPXHY2GFP/EP155和以G418为筛选标记、表达红色荧光蛋白的转化株pCPXG418RFP/EP155.将载体pCPXG418RFP转化pCPXHY2GFP/EP155,获得的转化株能观察到绿色荧光蛋白与红色荧光蛋白共定位的现象.板栗疫病菌绿色荧光与红色荧光共定位载体pCPXHY2GFP与pCPXG418RFP的构建,为深入研究病毒与宿主相互作用的分子机制提供了强有力的研究材料.     

GFP基因在棉花转化中的应用

以绿色荧光蛋白GFP基因为报道基因,用花粉管通道和农杆菌介导的转化方法将外源基因导入棉花（Gossypium hirsutum L.)分别获得转化幼胚,幼苗和转化愈伤组织,用手持紫外灯结合显微镜检术能够快速地对转化子进行活体筛选鉴定,比用GUS检测广阔圾明显的优越性,本研究不但为花粉管道道转化法的可行性提供了新的证据。同时也建立了GFP用于棉花基因工程研究的检测技术体系。     

Rapid Diffusion of Green Fluorescent Protein in the Mitochondrial Matrix

Abstract. It is thought that the high protein density in the mitochondrial matrix results in severely restricted solute diffusion and metabolite channeling from one enzyme to another without free aqueous-phase diffusion. To test this hypothesis, we measured the diffusion of green fluorescent protein (GFP) expressed in the mitochondrial matrix of fibroblast, liver, skeletal muscle, and epithelial cell lines. Spot photobleaching of GFP with a 100× objective (0.8-μm spot diam) gave half-times for fluorescence recovery of 15–19 ms with >90% of the GFP mobile. As predicted for aqueous-phase diffusion in a confined compartment, fluorescence recovery was slowed or abolished by increased laser spot size or bleach time, and by paraformaldehyde fixation. Quantitative analysis of bleach data using a mathematical model of matrix diffusion gave GFP diffusion coefficients of 2–3 × 10⁻⁷ cm²/s, only three to fourfold less than that for GFP diffusion in water. In contrast, little recovery was found for bleaching of GFP in fusion with subunits of the fatty acid β-oxidation multienzyme complex that are normally present in the matrix. Measurement of the rotation of unconjugated GFP by time-resolved anisotropy gave a rotational correlation time of 23.3 ± 1 ns, similar to that of 20 ns for GFP rotation in water. A rapid rotational correlation time of 325 ps was also found for a small fluorescent probe (BCECF, ~0.5 kD) in the matrix of isolated liver mitochondria. The rapid and unrestricted diffusion of solutes in the mitochondrial matrix suggests that metabolite channeling may not be required to overcome diffusive barriers. We propose that the clustering of matrix enzymes in membrane-associated complexes might serve to establish a relatively uncrowded aqueous space in which solutes can freely diffuse.     

绿色荧光蛋白及其在植物分子生物学研究中的应用

绿色荧光蛋白(GFP)是海洋生物水母(Aequoria victoria)体内的一种发光蛋白,近十年来成为在生物化学和细胞生物学研究和应用中用得最广泛的蛋白质之一。文章就绿色荧光蛋白的特性及其在植物分子生物学中应用的研究进展作了概述。     

绿色荧光蛋白在植物细胞生物学中的应用

克隆于海洋动物水母 (Ａｅｑｕｏｒｅａｖｉｃｔｏｒｉ ａ)的绿色荧光蛋白 (ｇｒｅｅｎｆｌｕｏｒｅｓｃｅｎｔｐｒｏｔｅｉｎ ,ＧＦＰ)作为一种新型的非酶性报告基因具有检测简便 ,结果真实可靠 ,不需要任何外源底物或辅助因子的特点 ,自出现以来它已引起人们的广泛兴趣 ,目前已经应用于烟草、柑橘、拟南芥、玉米、水稻、大豆、苜蓿等多种植物材料的研究中。ＧＦＰ含有特殊的六肽生色团结构 ,用蓝紫光激发即能发出肉眼清晰可见的绿色荧光 ,而无需任何底物或辅助因子。ＧＦＰ能与多种不同蛋白质的Ｎ端或Ｃ端融合而保持与天然蛋白质相似的荧…