Thiol-specific probes indicate that the beta-chain of platelet glycoprotein Ib is a transmembrane protein with a reactive endofacial sulfhydryl group.
AuthorsKalomiris EL, Coller BS
JournalBiochemistry
PubMed ID2934089
We used two membrane-permeable fluorescent reagents, monobromobimane and N-[[5-(dimethylamino)-1-naphthalenyl]sulfonyl]aziridine (N-dansylaziridine), and one membrane-impermeable fluorescent probe, monobromo(trimethylammonio)bimane, all three of which react selectively with protein thiols, to assess the presence of reactive sulfhydryls in the platelet glycoprotein Ib (GPIb) molecule and establish the topology of any GPIb-reactive thiols in the platelet ... More
An allosteric mechanism controls antigen presentation by the H-2K(b) complex.
AuthorsGakamsky DM, Boyd LF, Margulies DH, Davis DM, Strominger JL, Pecht I
JournalBiochemistry
PubMed ID10508421
'The mechanism of assembly/dissociation of a recombinant water-soluble class I major histocompatibility complex (MHC) H-2Kb molecule was studied by a real-time fluorescence resonance energy transfer method. Like the H-2Kd ternary complex [Gakamsky et al. (1996) Biochemistry 35, 14841-14848], the interactions among the heavy chain, beta2-microglobulin (beta2m), and antigenic peptides were ... More
Rabbit polymorphonuclear neutrophils form 35S-labeled S-sulfo-calgranulin C when incubated with inorganic [35S]sulfate.
'Rabbit peritoneal polymorphonuclear neutrophils reduced inorganic [35S]sulfate to [35S]sulfite in vitro, concomitant with incorporation of 35S into a 10.68-kDa cytosolic protein as a S-[35S]sulfo-derivative. Amino-terminal sequencing of the purified protein identified calgranulin C, a member of the S100 protein family. cDNA clones of calgranulins B and C were isolated using ... More
Intracellular EDTA mimics parvalbumin in the promotion of skeletal muscle relaxation.
AuthorsJohnson JD, Jiang Y, Rall JA
JournalBiophys J
PubMed ID10049331
'Parvalbumin (PA) is an intracellular Ca2+-binding protein found in some muscle and nerves. Its ability to bind Ca2+ and facilitate skeletal muscle relaxation is limited by its Mg2+ off-rate. EDTA serves as an "artificial" PA in that it exhibited similar rate constants for Mg2+ (3 s-1) and Ca2+ (0.7 s-1) ... More
S-(N-dansylaminoethyl)-6-mercaptoguanosine as a fluorescent probe for the uridine transport system in human erythrocytes.
AuthorsShohami E, Koren R
JournalBiochem J
PubMed ID444216
'A fluorescent derivative of 6-mercaptoguanosine, S-(N-dansylaminoethyl)-6-mercaptoguanosine, was synthesized, and found to be a strong inhibitor of the uridine transport system of erythrocyte (Ki approximately 0.3 microM). The emission spectrum of this compound has peaks at 400 and 550 nm. The emission at 550, but not that a 400 nm, in ... More
Isoform specific interactions of troponin I and troponin C determine pH sensitivity of myofibrillar Ca2+ activation.
AuthorsBall KL, Johnson MD, Solaro RJ
JournalBiochemistry
PubMed ID8031779
'We investigated whether differences in isoforms of troponin I (TnI) and troponin C (TnC) can account for the greater inhibition of Ca(2+)-dependent MgATPase activity by acidic pH in cardiac (c) than in fast skeletal (fs) myofilaments. We studied fast skeletal myofibrils from which whole Tn was extracted by displacement with ... More
The effects of phosphorylation of cardiac troponin-I on its interactions with actin and cardiac troponin-C.
Authorsal-Hillawi E, Bhandari DG, Trayer HR, Trayer IP
JournalEur J Biochem
PubMed ID7737201
'It is known that the phosphorylation of two serine residues on the NH2-terminal extension specific to cardiac troponin-I (Tn-I) modulates the calcium-dependent activation of the myofilaments. The process by which this occurs remains an unsolved puzzle. We have applied a dissective approach to study the effect of this phosphorylation on ... More
Binary interactions of troponin subunits.
AuthorsIngraham RH, Swenson CA
JournalJ Biol Chem
PubMed ID6204984
'The association constants for the formation of the binary complexes of rabbit fast skeletal muscle troponin subunits have been determined for three solution conditions: (a) 1 mM CaCl2, (b) 3 mM MgCl2 and 1 mM EGTA, and (c) 2 mM EDTA. The subunits were labeled with extrinsic fluorescence probes, either ... More
Ligand-induced changes in the accessibility of sulphydryl groups of Neurospora crassa pyruvate kinase.
AuthorsKapoor M, Parfett CL
JournalInt J Biochem
PubMed ID154420
Derivatization of thiol-containing compounds.
AuthorsShimada K, Mitamura K
JournalJ Chromatogr B Biomed Appl
PubMed ID7820279
'The determination of thiol-containing compounds in biological fluids is important in biochemistry and clinical chemistry. In this paper, derivatization reagents for thiols are reviewed with respect to their reactivity, selectivity, spectroscopic characteristics and their applicability especially to high-performance liquid chromatography. Derivatization used in ultraviolet and electrochemical detection. The derivatization reagents ... More
Dansylaziridine-labeled troponin C. A new fluorescent "physiological" probe for calcium regulation by sarcoplasmic reticulum.
AuthorsJohnson JD, Schwartz A
JournalJ Biol Chem
PubMed ID670191
'Dansylaziridine-labeled troponin C (TnCDANZ) undergoes a greater than 2-fold fluorescence enhancement with Ca2+ binding to the Ca2+-specific regulatory sites of troponin C. Hence, TnCDANZ serves as a very good indicator of Ca2+ in the range of 3.0 to 70 micron. Ca2+ uptake and release by sarcoplasmic reticulum can be easily ... More
Bovine serum albumin as a catalyst. VI. Specificity of several nucleophilic groups in the protein for N-dansylaziridine.
AuthorsSturgill TW, Baskin GS, Taylor RP
JournalBiochim Biophys Acta
PubMed ID911863
'The reaction of N-dansylaziridine with serum albumin (both bovine and human) results in incorporation of about 3 mol of covalently bound dansyl label per mol protein. This indicates that a number of nucleophilic groups in these proteins (in addition to the free sulfhydryl group) will react with this reagent. The ... More
Modification of acetylcholinesterase with N-dansylaziridine.
AuthorsMutus B, Tomlinson G, Duncan DV
JournalBiochem Biophys Res Commun
PubMed ID7317044
A fluorescence stopped flow analysis of Ca2+ exchange with troponin C.
AuthorsJohnson JD, Charlton SC, Potter JD
JournalJ Biol Chem
PubMed ID429366
Interaction of skeletal myosin light chains with calcium ions.
AuthorsAlexis MN, Gratzer WB
JournalBiochemistry
PubMed ID678511
Fluorimetric studies of actin labeled with dansyl aziridine.
AuthorsLin TI
JournalArch Biochem Biophys
PubMed ID147051
Preparation of fluorescent labeled calmodulins.
AuthorsOlwin BB, Storm DR
JournalMethods Enzymol
PubMed ID6316073
Calcium-dependent and calcium-independent affinities of calmodulin for calmodulin-binding proteins determined by fluorescence techniques.
AuthorsOlwin BB, Keller CH, Storm DR
JournalAdv Cyclic Nucleotide Protein Phosphorylation Res
PubMed ID6326526
Dansylaziridine-labeled troponin C. A fluorescent probe of Ca2+ binding to the Ca2+-specific regulatory sites.
AuthorsJohnson JD, Collins JH, Potter JD
JournalJ Biol Chem
PubMed ID681361
Fluorescence dynamics studies of troponin C.
AuthorsSteiner RF, Norris L
JournalBiopolymers
PubMed ID3620580
Fluorescent conjugates of albumins as potential new reagents for the determination of bilirubin and its reserve binding capacity in body fluids.
AuthorsNavon G, Panigel R
JournalClin Chim Acta
PubMed ID759050
Use of beta-cyclodextrin fluorophore complexes to improve the efficiency of fluorescent label incorporation into proteins.
AuthorsKinsland LN, Wiechelman KJ
JournalJ Biochem Biophys Methods
PubMed ID6725851
Fluorescence energy transfer studies of skeletal troponin C proximity between methionine-25 and cysteine-98.
AuthorsCheung HC, Wang CK, Garland F
JournalBiochemistry
PubMed ID7171543
Comparison of the kinetic properties of troponin-C and dansylaziridine-labeled troponin-C1.
AuthorsIio T, Kondo H
JournalJ Biochem (Tokyo)
PubMed ID7419512
Comparison of the kinetic properties of troponin-C and dansylaziridine-labeled troponin-C revealed that the calcium ion binding and removal reactions with the low affinity Ca2+-binding sites (sites I and II) and the resultant local conformational change are rapid processes, and that the calcium ion binding and removal reactions with the high ... More
Chemical modification of rabbit IgG with N-dansylaziridine. Investigation of the properties of dansylated antibodies.
AuthorsPikuleva IA, Turko IV, Adamovich TB, Chashchin VL
JournalMol Immunol
PubMed ID2062314
To elucidate the effect of antigen binding fluorescent thiol reagent, N-dansylaziridine (DAZ), which is sensitive to the changes in the microenvironment, was used for modification of rabbit IgG hinge region cysteine residue. DAZ binds to hinge region Cys 226 as evidenced by the structural analysis. Labelling of IgG with DAZ ... More
Equilibrium titration of protein-ligand binding affinity in the presence of volatile reagents--a semiautomated approach.
AuthorsBreukelmann D, Housmans PR
JournalAnal Biochem
PubMed ID12576062
An existing method of equilibrium titration was significantly improved for investigating the effects of volatile anesthetics on Ca(2+) binding characteristics of human recombinant cardiac troponin C in in vitro conditions. The modified method increases stability of volatile compound concentrations in solution and allows for faster and more accurate data acquisition. ... More
Fluorescence titration and fluorescence stopped-flow studies on skeletal muscle troponin labeled with fluorescent reagent.
AuthorsIio T, Kondo H
JournalJ Biochem (Tokyo)
PubMed ID7174641
Incorporation of skeletal muscle troponin C (TN-C) subunit into skeletal muscle troponin (TN) induces a large increase in the apparent binding constant of Ca2+ to the low affinity Ca2+-binding sites of TN-C (from 1 X 10(5) M-1 to 5.6 X 10(6) M-1 in the presence of 2 mM MgCl2), and ... More
The interaction of melittin with troponin C.
AuthorsSteiner RF, Norris L
JournalArch Biochem Biophys
PubMed ID3579303
Melittin has been found to interact with troponin C with high affinity in the presence of Ca2+. The association constant approaches in magnitude that for melittin and calmodulin. The interaction results in a shift to lower wavelengths of the emission band of Trp-19 of melittin and in an increased shielding ... More
Viral capsid mobility: a dynamic conduit for inactivation.
AuthorsBroo K, Wei J, Marshall D, Brown F, Smith TJ, Johnson JE, Schneemann A, Siuzdak G
JournalProc Natl Acad Sci U S A
PubMed ID11226229
Mass spectrometry and fluorescent probes have provided direct evidence that alkylating agents permeate the protein capsid of naked viruses and chemically inactivate the nucleic acid. N-acetyl-aziridine and a fluorescent alkylating agent, dansyl sulfonate aziridine, inactivated three different viruses, flock house virus, human rhinovirus-14, and foot and mouth disease virus. Mass ... More
Ca2+-specific fluorescence changes in N-dansylaminoethyl-labelled oncomodulin.
AuthorsMutus B, Flohr EJ, MacManus JP
JournalCan J Biochem Cell Biol
PubMed ID4075234
Rat oncomodulin (isoelectric point (pI) = 3.9) and homologous carp parvalbumin (pI = 3.95) was labelled at Cys-18 which is located in the AB loop, with the fluorescent reagent N-dansylaziridine. The fluorescence spectrum of the labelled parvalbumin was insensitive to both Mg2+ and Ca2+ binding. In contrast the dansyl fluorescence ... More
Specific proteolysis regulates fusion between endocytic compartments in Xenopus oocytes.
AuthorsOpresko LK, Karpf RA
JournalCell
PubMed ID3315227
We examined the role of proteolytic ligand modification in endosomal targeting using vitellogenin (VTG) uptake by Xenopus oocytes as a model system. Non-cleavable VTG is internalized, but does not appear in yolk platelets. We identified two inhibitors of VTG processing into the yolk proteins: the ionophore monensin and pepstatin A, ... More
Fluorescence changes from single striated muscle fibres injected with labelled troponin C (TnCDANZ).
AuthorsGriffiths PJ, Potter JD, Coles B, Strang P, Ashley CC
JournalFEBS Lett
PubMed ID6489515
A fluorescently labelled derivative of the calcium binding subunit of troponin, TnC, has been injected into isolated striated muscle fibres from the barnacle Balanus nubilus. The Ca2+ affinity of isolated TnC is close to that of intact troponin when located in the thin filament. Excitation of the TnCDANZ within the ... More
Fluorescence energy-transfer studies on the pyruvate dehydrogenase complex isolated from Azotobacter vinelandii.
AuthorsScouten WH, De Graaf-Hess AC, De Kok A, Grande HJ, Visser AJ, Veeger C
JournalEur J Biochem
PubMed ID348464
Fluorescence energy transfer has been employed to estimate the minimum distance between each of the active sites of the 4 component enzymes of the pyruvate dehydrogenase multienzyme complex from Azotobacter vinelandii. No energy transfer was seen between thiochrome diphosphate, bound to the pyruvate decarboxylase active site, and the FAD of ... More
Ca(2+)-dependence of structural changes in troponin-C in demembranated fibers of rabbit psoas muscle.
AuthorsAllen TS, Yates LD, Gordon AM
JournalBiophys J
PubMed ID1547328
The Ca(2+)-dependence of structural changes in troponin-C (TnC) has been detected by monitoring the fluorescence from TnC labeled at Methionine-25, in the NH2-terminal domain, with danzylaziridine (TnC-DANZ) and then exchanged for endogenous TnC in glycerinated single fibers. The fluorescence-pCa relation obtained from fibers stretched to a sarcomere length greater than ... More
Studies on the spatial arrangement of muscle thin filament proteins using fluorescence energy transfer.
AuthorsLin TI, Dowben RM
JournalJ Biol Chem
PubMed ID6682103
The distance between a pair of fluorophores attached to Cys-36 of beta-tropomyosin and Cys-373 of actin in reconstituted muscle thin filaments was measured by fluorescence energy transfer. Two pairs of donor/acceptor fluorophores, N-(iodoacetylaminoethyl)-5-naphthylamine-1-sulfonic acid/5-iodoacetamidofluorescein and N-(1-pyrene)maleimide/dimethylamino-4-maleimidostilbene, were covalently attached to tropomyosin and actin. The energy transfer efficiencies in various reconstituted ... More
Fluorescence resonance energy transfer measurements of distances in actin and myosin. A critical evaluation.
Authorsdos Remedios CG, Miki M, Barden JA
JournalJ Muscle Res Cell Motil
PubMed ID3298315
The contractile proteins actin and myosin are of considerable biological interest. They are essential for muscle contraction and in eukaryotic cells they play a crucial role in most contractile phenomena. Over the years since the first fluorescence resonance energy transfer (FRET) paper appeared, an extensive body of literature has accumulated ... More
Calcium binding and fluorescence measurements of dansylaziridine-labelled troponin C in reconstituted thin filaments.
AuthorsZot HG, Potter JD
JournalJ Muscle Res Cell Motil
PubMed ID3429643
The direct binding of Ca2+ to reconstituted thin filaments containing troponin C and the 5-dimethylaminonaphthalene-1-sulphonylaziridine (DANZ) fluorescent analogue of troponin C (TnCDANZ) was measured (25 degrees C) at three Mg2+ concentrations. Biphasic Scatchard plots were found for all binding curves reflecting the binding of Ca2+ to high- and low-affinity sites ... More
Calcium-induced troponin flexibility revealed by distance distribution measurements between engineered sites.
The contraction of vertebrate striated muscle is regulated by Ca2+ binding to troponin C (TnC). This causes conformational changes which alter the interaction of TnC with the inhibitory protein TnI and the tropomyosin-binding protein TnT. We have used the frequency domain method of fluorescence resonance energy transfer to measure TnT-TnC ... More
Conformational changes of 30S ribosomes measured by intrinsic and extrinsic fluorescence.
AuthorsSpitnik-Elson P, Schechter N, Abramovitz R, Elson D
JournalBiochemistry
PubMed ID793614
The intrinsic tryptophan fluorescence and the fluorescence of N-(3-pyrene)maleimide, a covalently bound sulfhydryl-specific extrinsic probe, have been used to study the conformation of the 30S ribosomal subunit of Escherichia coli. (a) The tryptophan fluorescenct spectrum of the free ribosomal proteins is shifted to shorter wavelengths than that of free tryptophan. ... More
Interaction of a fluorescent N-dansylaziridine derivative of troponin I with calmodulin in the absence and presence of calcium.
AuthorsOlwin BB, Keller CH, Storm DR
JournalBiochemistry
PubMed ID6293554
Rabbit skeletal muscle troponin I was covalently labeled with N-dansylaziridine, resulting in a fluorescent labeled protein. This derivative (DANZTnI) and native troponin I (TnI) inhibited calmodulin (CaM) stimulation of bovine heart Ca2+-sensitive cyclic nucleodite phosphodiesterase with identical inhibition constants. Association of DANZTnI with calmodulin was monitored directly by changes in ... More
Determination of the free-energy coupling for binding of calcium ions and troponin I to calmodulin.
AuthorsKeller CH, Olwin BB, LaPorte DC, Storm DR
JournalBiochemistry
PubMed ID7059575
Regulation of a wide variety of biological systems by Ca2+ is now known to be mediated through calmodulin, a Ca2+-binding protein. Calmodulin forms Ca2+-dependent complexes with several proteins, including troponin I. We have determined the free-energy coupling (delta GoCT) for binding of Ca2+ and troponin I to calmodulin by measuring ... More
Fast skeletal muscle skinned fibers and myofibrils reconstituted with N-terminal fluorescent analogues of troponin C.
AuthorsZot HG, Güth K, Potter JD
JournalJ Biol Chem
PubMed ID2946678
Glycerinated rabbit fast skeletal muscle fibers were chemically skinned with 1% Brij 35 and partially depleted of endogenous troponin C subunit (TnC) by exposure of the fibers to EDTA (Zot, H. G., and Potter, J. D. (1982) J. Biol. Chem. 257, 7678-7683). The TnC-depleted fibers exhibited a decrease in maximal ... More
Properties of troponin C acetylated at lysine residues.
AuthorsGrabarek Z, Mabuchi Y, Gergely J
JournalBiochemistry
PubMed ID7547922
We have studied the properties of rabbit skeletal troponin C (TnC) fully acetylated at its lysine residues (AcTnC). Acetylation causes a decrease in thermal stability of both domains of TnC in the absence of Ca2+. At 25 degrees C, the acetylated C-terminal domain of TnC is almost completely unfolded and ... More
Distance distributions and anisotropy decays of troponin C and its complex with troponin I.
AuthorsCheung HC, Wang CK, Gryczynski I, Wiczk W, Laczko G, Johnson ML, Lakowicz JR
JournalBiochemistry
PubMed ID2036391
We used frequency domain measurements of fluorescence resonance energy transfer to recover the distribution of distances between Met 25 and Cys 98 in rabbit skeletal troponin C. These residues were labeled with dansylaziridine as energy donor and 5-(iodoacetamido)eosin as acceptor and are located on the N- and C-terminal lobes of ... More
Troponin I enhances acidic pH-induced depression of Ca2+ binding to the regulatory sites in skeletal troponin C.
Authorsel-Saleh SC, Solaro RJ
JournalJ Biol Chem
PubMed ID2830278
Inhibition of muscle force development by acidic pH is a well known phenomenon, yet the exact mechanism by which a decrease in pH inhibits the Ca2+-activated force in striated myofilaments remains poorly understood. Whether or not the deactivation by acidic pH involves direct competition between Ca2+ and protons for regulatory ... More
Ca2+ and cross-bridge-induced changes in troponin C in skinned skeletal muscle fibers: effects of force inhibition.
AuthorsMartyn DA, Freitag CJ, Chase PB, Gordon AM
JournalBiophys J
PubMed ID10049329
Changes in skeletal troponin C (sTnC) structure during thin filament activation by Ca2+ and strongly bound cross-bridge states were monitored by measuring the linear dichroism of the 5' isomer of iodoacetamidotetramethylrhodamine (5'IATR), attached to Cys98 (sTnC-5'ATR), in sTnC-5'ATR reconstituted single skinned fibers from rabbit psoas muscle. To isolate the effects ... More
Muscle cross-bridge attachment: effects on calcium binding and calcium activation.
AuthorsGordon AM, Ridgway EB, Yates LD, Allen T
JournalAdv Exp Med Biol
PubMed ID3261497
Data from intact and skinned muscle fibers support the hypothesis that cross-bridge interaction modifies TnC structure and calcium activation. Barnacle single muscle fibers microinjected with the calcium bioluminescent photoprotein, aequorin, show extra light (calcium) when shortened during the declining phase of the calcium transient. The extra calcium is increased by ... More
Direct, real-time measurement of rapid inorganic phosphate release using a novel fluorescent probe and its application to actomyosin subfragment 1 ATPase.
AuthorsBrune M, Hunter JL, Corrie JE, Webb MR
JournalBiochemistry
PubMed ID8031761
A probe has been developed that can rapidly measure micromolar concentrations of inorganic phosphate (Pi), in particular to follow the release of Pi in real time from enzymes such as phosphatases. Its application is described to investigate the mechanism of actomyosin subfragment 1 ATPase. The probe uses the A197C mutant ... More
Ca2+, pH and the regulation of cardiac myofilament force and ATPase activity.
AuthorsSolaro RJ, el-Saleh SC, Kentish JC
JournalMol Cell Biochem
PubMed ID2530435
When the pH surrounding myofilaments of striated muscle is reduced there is an inhibition of both the actin-myosin reaction as well as the Ca2+-sensitivity of the myofilaments. Although the mechanism for the effect of acidic pH on Ca2+-sensitivity has been controversial, we have evidence for the hypothesis that acidic pH ... More
Reciprocal coupling between troponin C and myosin crossbridge attachment.
AuthorsZot AS, Potter JD
JournalBiochemistry
PubMed ID2790028
The attachment of cycling myosin crossbridges to actin and the resultant muscle contraction are regulated in skeletal muscle by the binding of Ca2+ to the amino-terminal, regulatory sites of the troponin C (TnC) subunit of the thin filament protein troponin. Conversely, the attachment of crossbridges to actin has been shown ... More
Location of a contact site between actin and myosin in the three-dimensional structure of the acto-S1 complex.
AuthorsKasprzak AA, Chaussepied P, Morales MF
JournalBiochemistry
PubMed ID2532548
Using fluorescence resonance energy transfer (FRET), we measured distances from chromophores located at or near the actin-binding stretch of amino acids 633-642 of myosin subfragment 1 (S1), to five points in the acto-S1 complex. Specific labeling of this site was achieved by first attaching the desired chromophore to an "antipeptide" ... More
Fluorescent probes attached to Cys 35 or Cys 84 in cardiac troponin C are differentially sensitive to Ca(2+)-dependent events in vitro and in situ.
AuthorsPutkey JA, Liu W, Lin X, Ahmed S, Zhang M, Potter JD, Kerrick WG
JournalBiochemistry
PubMed ID9020797
The goal of the current study was to generate recombinant cTnC proteins with single Cys residues as sites for attachment of fluorescent probes that can distinguish between the structural effects of myosin cross bridges and direct Ca2+ binding to cTnC (cardiac and slow skeletal troponin C) in skinned fibers. We ... More
Characterizing the response of calcium signal transducers to generated calcium transients.
AuthorsDavis JP, Tikunova SB, Walsh MP, Johnson JD
JournalBiochemistry
PubMed ID10194340
Cellular Ca2+ transients and Ca2+-binding proteins regulate physiological phenomena as diverse as muscle contraction, neurosecretion, and cell division. When Ca2+ is rapidly mixed with slow Ca2+ chelators, EGTA, or Mg2+/EDTA, artificial Ca2+ transients (ACTs) of varying duration (0.1-50 ms half-widths (hws)) and amplitude can be generated. We have exposed several ... More
Kinetic studies of calcium and magnesium binding to troponin C.
AuthorsRosenfeld SS, Taylor EW
JournalJ Biol Chem
PubMed ID3965449
The kinetic mechanism of calcium binding was investigated for the high-affinity calcium-magnesium sites of troponin C (TN-C), for the C-terminal fragment containing only the high-affinity sites (TR2) and for the TN-C:TN-I (where TN-I represents the inhibitory subunit of troponin) complex. Rate constants were measured by the change in fluorescence of ... More