Fluorescent labeling of proteins in sodium dodecyl sulfate complexes with fluorescamine

The effects of sodium dodecyl sulfate on the fluorescent labeling of proteins were studied. Of 57 primary amine groups in bovine serum albumin, no more than 7 are titrable by fluorescamine. Fluorescamine labeling does not cause appreciable conformational changes of proteins. The extent of labeling of proteins decreases as the concentrations of sodium dodecyl sulfate increases. The fluorescence properties of labeled primary amine are only slightly affected by the polarities of the solvents. The inhibitory effects of sodium dodecyl sulfate upon labelings are interpreted as the low permeability of fluorescamine toward the highly charged envelopes of sodium dodecyl sulfate-protein micelles.     

Abundance of protein-bound sulfhydryl and bisulfide groups at chromosomal nucleolus organizing regions

Silver stainability of the chromosomal nucleolus organizing regions that contain the structural genes for ribosomal RNA can be abolished by proteolytic and oxidative treatments. Histone extraction has no effect. This indicates that reducing groups of non-histone chromosomal proteins are responsible for silver staining. Treatment with fluorescent sulfhydryl and disulfide specific reagents followed by silver staining demonstrates coincidence of silver dots and brightly fluorescent spots at the short arms of human acrocentric chromosomes where ribosomal RNA-genes are located. After treatment with cupric sulfite reagent in the presence of urea fluorescence and silver staining was no longer possible. Silver staining has been reported to be associated with ribosomal RNA-gene activity. Acrocentric chromosomes that are negative in silver staining also lack the brightly fluorescent spots. Therefore, we conclude that an abundance of protein-bound sulfhydryl and disulfide groups occur at nucleolar organizing regions with active genes. Differentially fluorescing spots could not be observed after staining with fluorescamine. So, either the sulfhydryl reagents used in this study are much more sensitive than fluorescamine to study protein distributions in cytological preparations, or our observations point to a local accumulation of some specific protein(s) rich in sulfhydryls. The presence of many sulfhydryl and disulfide groups at the nucleolus organizing regions seems suggestive of a great flexibility of protein(s) by transition of sulfhydryl groups to disulfide bridges and vice versa at these highly active regions of the genome.     

Application of fluorescamine to the study of protein-DNA interactions.

The reactivity of alpha-amino groups of basic proteins towards fluorescamine is essentially abolished if salt linkages with DNA phosphate groups are formed. This observation prompted the elaboration of a very general assay which allows the determination of binding parameters for the interaction of proteins with DNA and chromatin. Protamines, labeled with fluorescamine prior to their binding by DNA appear to be useful probes to monitor the formation and nature of DNA-protein complexes.     

Labeling of membranes from erythrocytes and corn with fluorescamine

Fluorescamine was used as a fluorescent label for intact human erythrocytes and slices of corn coleoptile tissue. This reagent has a greater affinity for membranous than for soluble proteins, and also labels membrane lipids which contain primary amine groups. In addition, some membrane fractions from labeled coleoptiles have a higher affinity for fluorescamine than do others. The relative labeling of the various fractions can be altered by changing the pH of the external labeling medium. Because the pH of the medium determines the rate of hydrolysis of fluorescamine to an unreactive form, this result suggests that the specificity of this reagent towards different cellular structures is determined by the lifetime of the active reagent. Fluorescamine was not found to be a specific reagent for the cell surface.     

In situ antigen localization with fluorescamine-conjugated antibodies: a new method.

A simple and rapid procedure for the preparation of fluorescent antibodies with fluorescamine is described. The major advantage of the method is that labeled antibody requires no further purification following conjugation. The utility of the method is illustrated by fluorescent staining of virus-specific cytoplasmic and nuclear antigens, those of vesicular stomatitis virus and adenovirus, respectively. The intensity of fluorescence permits short photographic exposure times, and the stained preparations have retained their fluorescence for more than 9 months.     

The relationship of molecular weight to electrophoretic mobility of fluorescamine-labeled proteins in polyacrylamide gels

Proteins of known molecular weights were labeled with fluorescamine and then subjected to electrophoresis through polyacrylamide gels. The electrophoretic mobilities of the fluorescamine-labeled proteins were dependent upon their respective molecular weights over a range of 17,000 to 70,000 daltons. The correlation of electrophoretic mobility of fluorescamine-labeled protein to molecular weight was similar to results obtained in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The speed with which data can be obtained with the described procedure is a definite advantage over currently employed procedures. These findings encourage the use of fluorescamine for rapid, sensitive determinations of molecular weights of proteins in polyacrylamide gels.     

利用荧光蛋白标记西瓜枯萎病菌的过氧化物酶体及细胞核

西瓜枯萎病是一种世界范围的西瓜毁灭性病害,其病原菌为尖孢镰刀菌西瓜专化型(Fusarium oxysporum f.sp.niveum,FON)。研究病原菌生长发育和侵染的机制是解决病害的根本途径。利用荧光蛋白对细胞或细胞器进行标记,是病原菌研究中的重要方法。该研究利用绿色荧光蛋白和红色荧光蛋白对FON的细胞核和过氧化物酶体进行了荧光标记。通过农杆菌介导转化(Agrobacterium tumefaciens-mediated transformation,AtMT),该文将3种不同的荧光定位载体分别导入FON,获得了细胞核红色荧光标记的转化子(潮霉素抗性,含mCherry-H2B融合蛋白),以及过氧化物酶体绿色(潮霉素抗性,含GFP-PTS1融合蛋白)和红色(潮霉素抗性,含DsRED-PTS1融合蛋白)荧光标记的转化子各1种。在标记细胞核的菌株中,菌丝、孢子都可见明亮、圆形的红色荧光点,荧光点与DAPI染色标记的细胞核区域完全重合。在过氧化物酶体标记的菌株中,菌丝、孢子中可见明亮的红色或绿色荧光成小点状分布,符合过氧化物酶体的分布特征,而且在脂类物质诱导的条件下,荧光点的数量明显增加。此外,该文还利用细胞壁荧光染色剂卡氏白对3种荧光蛋白标记菌株进行染色。结果显示,卡氏白染色产生的蓝色荧光与红、绿荧光蛋白的荧光在FON中互不干扰。转化子继代培养和初步分析表明,其表型与野生型无差异,菌株继代后荧光表达稳定、定位明显。该结果为进一步研究FON细胞器动态、生长发育与致病分子机制提供了方法和工具。     

Live-cell microscopy of single nuclear chromosomes and genome compartments: evaluation of labeling procedure and imaging conditions.

BACKGROUND: Single chromosomes and genome compartments in nuclei of living mammalian cells can be analyzed microscopically after specific labeling with fluorescent dyes. This is achieved by incorporating fluorescent nucleotides into the chromosomal DNA during replication (Zink et al.: Hum Genet 102:241-251, 1998; Manders et al.: J Cell Biol 144:813-821, 1999; Sadoni et al.: J Cell Biol 146:1211-1226, 1999). We characterized the potential artificial impact of this approach on chromosome structure and dynamics. We also evaluated potential sources of artifacts in corresponding live-cell imaging. MATERIALS AND METHODS: The subchromosomal distribution of labeled DNA was analyzed, and the fate of labeled nucleotides within cell nuclei was studied. Cell-cycle parameters were used to analyze cell function after incorporation of fluorescent nucleotides. The influences of phototoxic effects on cell division and morphology were studied. RESULTS: Fluorescent nucleotides were only incorporated for a restricted time period during S-phase, and a uniform labeling of chromosomal DNA could not be achieved. Fluorescent nucleotides incorporated into the DNA showed no or only mild effects on cell growth. Cell-cycle parameters and cellular morphology were valuable indicators for proper cell function during live-cell imaging. CONCLUSIONS: There is no indication for a substantial impairment of cellular functions if fluorochromes are covalently linked to chromosomal DNA. The controls we present for proper cell function during the imaging period are of general importance, as appropriate controls for live cell microscopy have not yet been well-defined.     

Induction of ion transport in rat heart mitochondria by fluorescamine

This report describes experimental results which show that the fluorescent reagent fluorescamine induces mitochondrial energy-independent swelling when the incubation media contain the chloride salts of the cations Li+, Na+, K+, Rb+, and Cs+. The reaction depends on the concentration of the dye and is inhibited by Mg2+, and its extension is closely related to the amount of the primary amino groups titrated by fluorescamine. Analysis of the labeled inner membrane in polyacrylamide gel shows that the amount of aminofluorescamine complex is lower when mitochondria are in the presence of Mg2+.     

Direct and Rapid Analysis of the Adhesion of Bacteria to Solid Surfaces: Interaction of Fluorescently Labeled Rhodococcus Strain GIN-1 (NCIMB 40340) Cells with Titanium-Rich Particles

A fluorimetric assay which enables direct and accurate analysis of the adhesion of bacteria to solid particles was developed. The assay is based on labeling of the bacteria with fluorescamine, which reacts with primary amino groups on the cell surface to yield a yellow fluorescence that is easily detectable by both fluorescence microscopy and spectrofluorimetry. As an example, fluorescent labeling of Rhodococcus strain GIN-1 (NCIMB 40340) cells enabled the detection and quantitative determination of their adsorption to TiO(inf2) and coal fly ash particles. Exposure of the cells to 10% acetone during the labeling reaction affected neither their viability nor their ability to adhere to these particles. Only a small fraction (^sim2%) of the total cell protein was labeled by fluorescamine upon staining of intact bacterial cells, which may indicate preferential labeling of certain proteins. Specificity studies carried out with the fluorescence assay confirmed previous findings that Rhodococcus strain GIN-1 cells possess high affinities for TiO(inf2), ZnO, and coal fly ash and low affinities for other metal oxides. In principle, the newly developed fluorimetric assay may be used for determination of cell adhesion to any solid matrix by either microscopic examination or epifluorescence measurements. In the present work, the adhesion of several other microorganisms to TiO(inf2) particles was tested as well, but their ability to adhere to these particles was significantly lower than that of Rhodococcus strain GIN-1 cells.     

Preparation and characterization of native, fluorescently labelled brain tubulin and microtubule-associated proteins (MAPs)

Tubulin and Microtubule-Associated Proteins (MAPs) isolated from chick brain by cycles of assembly and disassembly in vitro have been stoichiometrically labelled with the fluorogenic compound fluorescamine. Under the conditions employed, tubulin can be labelled with up to 2 moles of fluorescamine/mole of dimer while the MAPs accept up to 8 moles/mole of protein, assuming an average molecular weight of 300 000 D. After the labelling procedure, both the tubulin and MAPs retain their native conformations as judged by several criteria: (a) the labelled proteins remain competent to participate in further rounds of the assembly-disassembly procedure in vitro, and the kinetics of this assembly are identical to those seen with an unlabelled control sample; (b) incubation of the fluorescent microtubule proteins with the antimitotic agent vinblastine sulfate results in the formation of birefringent vinblastine-tubulin paracrystals, indicating the binding site for this ligand is unaltered; (c) the mobilities of the fluorescent tubulin and MAPs on SDS-polyacrylamide gels are unaltered when compared to the mobilities of the respective unlabelled control proteins. The results are discussed in relation to the use of these fluorescent cytoskeletal proteins as easily detectable biochemical and histochemical probes.     

Location and purification of enzymes on polyacrylamide gels using dialyzable fluorescent markers

A method for the location of proteins/enzymes by polyacrylamide gel electrophoresis using dialyzable low-molecular-weight fluorescent peptide markers is described. The markers prepared by treating the peptic digest of casein with fluorescamine showed several bands on gel electrophoresis which helped in locating the proteins. The located desired protein could subsequently be purified by extraction.     

Structural components of mouse mammary tumor virus. II. Isolation and purification of virion polypeptides.

Mouse mammary tumor virus (MMTV) glycoproteins and nonglycosylated polypeptides were purified by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Primary amino groups were labeled with fluorescamine to enable visualization of MMTV polypeptides in the gels. Protein bands were sliced from the gels and eluted with 90 to 95% recovery. Eight MMTV polypeptides, including three of the major viral components as well as five minor proteins, were routinely obtained. Double diffusion assays and immunoelectrophoresis confirmed the retention of antigenicity identical to that of untreated MMTV virions. Antisera obtained from MMTV-free BALB/c mice immunized with these purified proteins reacted with the polypeptide immunogen as well as with detergent-disrupted MMTV virions from mouse milk or cell culture. Double diffusion assays using the specific mouse antisera failed to detect any cross-reactivity among the isolated polypeptides. A hemagglutination-inhibition assay demonstrated that the ability of MMTV virions to inhibit the hemagglutinating properties of influenza virus resides in the glycosylated polypeptides gp52, gp37.7, and gp33.     

Fluorescamine-labelled cortical fragments as a substrate for lysozyme and initiation protein (spore-lytic enzyme)

A fluorescamine assay for the detection of a spore-lytic enzyme from Clostridium perfringens is described. The substrate is prepared by treatment of cortical fragments with fluorescamine which reacts with amino terminal groups in the peptidoglycan which are not cross-linked, presumably diaminopimelic acid. Treatment of the labelled substrate with lytic enzymes results in the release of soluble fluorescent products which can be easily measured in a basic fluorometer. The assay is very sensitive, inexpensive and reproducible. As little as 1 μg of lysozyme can be detected by this assay.     

A new fluorescent microassay method for pepsin using succinyl-albumin.

A method was developed for fluorescent microassay of pepsin with a fluorescent reagent, fluorescamine, and a nonquenching substrate, succinyl-albumin. In this method hydrolysis of succinyl-albumin by pepsin at pH 2,0 was stopped by adding phosphate buffer, pH 6.1, and newly liberated amino groups in the reaction mixture were determined quantitatively by fluorescence after adding fluorescamine. Fluorescence increased linearly with 1.0 to 18 ng of hog pepsin. The assay was 200 times more sensitive than the modified micromethod of Anson [(1939) J. Gen. Phys.22, 79–89].     

Asymmetric labeling of amino lipids in liposomes.

Fluorescamine and trinitrobenzenesulfonate were used as chemical probes to differentially label amino phospholipids in liposomes. At low concentrations, fluorescamine reacts primarily with amino lipids on the external half of the bilayer. Further increase in fluorescamine concentration resulted in a linear increase of labeling indicating penetration and reaction with the internal half of the bilayer. Because of the pH requirements of the fluorescamine reaction, internal labeling was eliminated with a H+ gradient: inside acidic/outside alkaline. Differential labeling was also achieved with trinitrobenzenesulfonate, which is normally not permeable but which can be transported by valinomycin-K+ complex and react with internal amines. Thus, either half of the bilayer can be labeled with the same or different reagents. When liposomes were double-labeled, the fluorescence of fluorescamine was quenched by the trinitrobenzenesulfonate label. This quenching was reversed by solubilizing the liposomes with acidic ethanol. No quenching occurred when fluorescamine-labeled liposomes were mixed with trinitrobenzenesulfonate-reacted liposomes (or trinitrophenylated methylamine) suggesting close proximity of two labels is required for quenching. Conditions which promoted vesicular fusion promptly produced quenching. These differential labeling procedures can be usefully applied to quantitate aminolipids on internal and external vesicular surface, monitor vesicular fusion, and assess liposomal structure.     

Human erythrocyte damage at the initial stages of oxidative stress

Specific fluorescent probes have been used to monitor changes in erythrocyte membranes in the first stages of the hemolytic process induced by irradiation with visible light in the presence of protoporphyrin IX. Although no change, or even a slight increase of fluorescence anisotropy, occurred with two probes having a preferential binding to membrane proteins, such as fluorescamine and 3-pyrene maleimide, the fluorescence anisotropy of two lipophilic probes, namely diphenyl-hexatriene and anilino-naphtalene sulfonate, underwent a substantial decrease upon irradiation.     

An automated method for the fluorescamine reaction using a peristaltic pump.

An automated method is described for the measurement of amino acids and proteins by the fluorescamine reaction. Isopropanol is used as solvent for the fluorescamine, and all reagents are pumped by a peristaltic pump.     

The use of fluorescamine as a probe for labeling the outer surface of the plasma membrane

A rapid method was developed to label the outer surface of chick embryo fibroblasts with fluorescamine without disruption of the cell monolayer. Polyacrylamide gel electrophoresis resolved two distinct areas of fluorescence: a group of high molecular weight polypeptides and several rapidly migrating species. The latter were demonstrated by tlc to be phospholipids. Fluorescamine did not label internal components of the cell as evidenced by two intracellular proteins which were found to be non-fluorescent. Intact normal cells were labeled 3-fold more than transformed cells, indicating a possible loss of exposed sites at the surface, while disrupted cells, subsequently labeled, yielded similar amounts of fluorescence.     

Activation of 5-[125I]iodonaphthyl-1-azide via excitation of fluorescent (N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)) lipid analogs in living cells. A potential tool for identification of compartment-specific proteins and proteins involved in intracellular transport and metabolism of lipids

We describe a new technique for analysis of proteins located near fluorescent lipid analogs in intact living cells using the membrane-permeant, photoactivatable probe, 5-[125I]iodonaphthyl-1-azide ([125I]INA). [125I] INA can be activated directly with UV light or indirectly through excitation of adjacent fluorophores (photosensitizers) with visible light to modify nearby proteins covalently with 125I. In this report we demonstrate that fluorescent phospholipids and sphingolipids containing N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-6-aminocaproic acid serve as appropriate photosensitizers for [125I]INA. Using Chinese hamster ovary fibroblasts, we optimized the labeling conditions with respect to lipid concentration and time of irradiation and then examined the profiles of cellular proteins that were labeled when fluorescent analogs of ceramide, sphingomyelin, and phosphatidic acid were used as photosensitizers in living cells. The use of different fluorescent lipids, which label different subcellular compartments of cells as determined by fluorescence microscopy, derivatized different sets of cellular proteins with 125I. The labeled proteins were subsets of the total set of proteins available for derivatization as determined by direct activation of [125I]INA. Most proteins labeled by this procedure were pelleted by centrifugation of cell lysates at high speed (260,000 x g), but several soluble proteins were also labeled under these conditions. The implications of using this technique for identification of compartment-specific proteins and proteins involved in lipid metabolism and transport are discussed.