Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 54
Filter
1.
Schweiz Arch Tierheilkd ; 160(11): 641-648, 2018 Nov.
Article in German | MEDLINE | ID: mdl-30379131

ABSTRACT

INTRODUCTION: Between September 2016 and February 2017 a survey in Swiss deer farms were conducted to gain information about their husbandry. Questions about the business, feeding, management, health and deworming strategies were asked. 98 (19%) out of 527 registered farms (2016) participated in the survey. The farms were often run on a sideline business, had an average used agricultural area of 7.3 ha with an average of 38 deer. Pasture access was the preferred feeding strategy followed by offering first and second cut hay. Between 2013-2015 the most common causes of death were sudden death and injuries. Parasites were classified as no or rather small problem by 91 out of 102 deer owner. Fecal parasitological examinations of fecal samples were conducted in 36 (35%) of the responding farms. Gastrointestinal roundworms (Trichostrongylidae) were identified as the most common pathogens (in 42-59% of sampled farms), in addition large lungworms (Dictyocaulus sp.) and coccidia were detected. 45% of the participating farmers conducted at least one treatment against parasites between 2013 and 2015.


INTRODUCTION: Dans le but d'avoir une vue d'ensemble sur la détention du gibier d'élevage en Suisse, une enquête a été menée entre septembre 2016 et février 2017, comprenant des questions relatives à l'exploitation, à l'alimentation, à la situation sanitaire et aux stratégies en matière de vermifugation. 98 des 527 exploitations annoncées en 2016 (19%) ont participé à cette étude. Ces exploitations, qui constituent fréquemment un gain accessoire, avaient une surface agricole d'en moyenne 7,3 ha avec 38 cervidés. En matière d'alimentation, c'est le foin et le regain qui étaient le plus souvent utilisés en complément du pâturage. Les causes de pertes dans les troupeaux entre 2013 et 2015 étaient principalement les cas de mort subite ainsi que les blessures. 91 de 102 détenteurs de cervidés considéraient les parasites comme n'étant pas un problème ou n'étant qu'un faible problème. Des échantillons de selles, prélevés dans 36 (35%) des exploitations ayant répondu au questionnaire, montraient que les nématodes gastro-intestinaux (Trichostrongylidae) étaient les plus fréquents (présents dans 42-59% des exploitations testées); des vers pulmonaires (Dictyocaulus sp.) et des coccidies ont également été trouvés. Environ 45 % des détenteurs de cervidés ayant participé à l'enquête avaient effectué, dans la période comprise entre 2013 et 2015 au moins un traitement antiparasitaire.


Subject(s)
Animal Husbandry/statistics & numerical data , Deer , Farms/statistics & numerical data , Animal Husbandry/methods , Animals , Antiparasitic Agents/administration & dosage , Antiparasitic Agents/therapeutic use , Feces/parasitology , Humans , Parasitic Diseases, Animal/diagnosis , Parasitic Diseases, Animal/drug therapy , Parasitic Diseases, Animal/parasitology , Switzerland , Wounds and Injuries/veterinary
2.
Schweiz Arch Tierheilkd ; 166(6): 321-328, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38807435

ABSTRACT

INTRODUCTION: Two six-month old female Lacaune lambs with severe skeletal malformations of both front limbs were presented to the Department of Farm Animals, University of Zurich. The clinical examination showed alert animals with a high body weight and body condition score as well as a valgus deformation without pain or swelling. Radiographic examination showed severe irregularities in the epiphysial plate of the metacarpal bones in both lambs. Delayed growth in the lateral aspects of the physis was evident and resulted in valgus deformation. Nutritional causes were considered as the main reason for this presentation and a nutritional consultation was performed by the Institute of Animal Nutrition and Dietetics, University of Zurich. The estimated energy intake of these lambs was 65 % higher than the recommended maximum for growing sheep and the estimated vitamin D content of the diet was 71 % below the recommended allowance. Both animals were euthanized, and peripheral quantitative computed tomography (pQCT) was performed postmortem to measure total bone mineral density (BMD), trabecular bone mineral density (tBMD) and cortical bone mineral density (cBMD) of the left and right metatarsal bone of both animals. The BMD and the tBMD at 10 % of bone length were below the reference values and the BMD at 50 % was above the reference values. In addition, postmortem examination revealed a Salter-Harris-Typ-1 facture in the right caput humeri of one lamb. Histological evaluation showed defects in the articular cartilage with an eburnation in the metacarpal region and a disrupted area of columnar cartilage. This case report supports the fact that a high dietary energy intake leads to damage to the cartilage and the epiphyseal zone in sheep. In addition, insufficient dietary vitamin D intake contributed to the incomplete bone mineralization, as well as delayed growth and skeletal malformation.


INTRODUCTION: Deux agneaux Lacaune femelles de six mois présentant de graves malformations squelettiques des deux membres antérieurs ont été présentés au Département des animaux de rente de l'Université de Zurich. L'examen clinique a montré des animaux alertes avec un poids corporel et une note d'état corporel élevés ainsi qu'une déformation en valgus sans douleur ni gonflement. L'examen radiographique a montré de graves irrégularités dans la plaque épiphysaire des os métacarpiens chez les deux agnelles. Un retard de croissance du côté latéral de la physis était évident, entraînant une déformation en valgus. Des causes nutritionnelles ont été considérées comme étant la principale raison de cette situation et une consultation nutritionnelle a été effectuée par l'Institut de nutrition animale et de diététique de l'Université de Zurich. L'apport énergétique estimé de ces agneaux était supérieur de 65 % au maximum recommandé pour les moutons en croissance et la teneur estimée en vitamine D du régime alimentaire était inférieure de 71 % à l'apport recommandé. Les deux animaux ont été euthanasiés et une tomographie quantitative périphérique a été réalisée post mortem pour mesurer la densité minérale osseuse totale (DMO), la densité minérale osseuse trabéculaire (DMOt) et la densité minérale osseuse corticale (DMOc) des métatarses gauche et droit des deux animaux. La DMO et la DMOt à 10 % de la longueur de l'os étaient inférieures aux valeurs de référence et la DMO à 50 % était supérieure aux valeurs de référence. En outre, l'examen post-mortem a révélé une facture de Salter-Harris-Typ-1 dans le caput humeri droit d'un agneau. L'évaluation histologique a montré des défauts dans le cartilage articulaire avec une éburnation sousjacente dans la région métacarpienne et une zone de destruction du cartilage colonnaire. Ce rapport de cas confirme le fait qu'un apport énergétique alimentaire élevé entraîne des lésions du cartilage et de la zone épiphysaire chez les ovins. En outre, un apport alimentaire insuffisant en vitamine D a contribué à une minéralisation osseuse incomplète, ainsi qu'à un retard de croissance et à une malformation du squelette.


Subject(s)
Sheep Diseases , Animals , Female , Sheep , Sheep Diseases/pathology , Bone Density , Diet/veterinary
3.
Curr Opin Struct Biol ; 11(5): 516-22, 2001 Oct.
Article in English | MEDLINE | ID: mdl-11785750

ABSTRACT

Recently, new methods for determining time-evolving structures using infrared analogs of NMR spectroscopy have been introduced that have outstanding potential in structural biology. Already, within the past two years, structures of dipeptides, tripeptides and pentapeptides have been determined on much faster timescales than the conformational dynamics. Also, two-dimensional infrared correlation spectra of some proteins and isotopically edited alanine-rich helices have been examined.


Subject(s)
Oligopeptides/chemistry , Spectrophotometry, Infrared/methods , Models, Molecular , Molecular Structure , Nuclear Magnetic Resonance, Biomolecular , Protein Conformation , Spectroscopy, Fourier Transform Infrared
4.
J Mol Biol ; 163(1): 119-28, 1983 Jan 05.
Article in English | MEDLINE | ID: mdl-6834427

ABSTRACT

We report the successful observation of a picosecond transient difference spectrum in human nitrosylhemoglobin. The sample (23 degrees C) is excited with an approximately 8 ps, approximately 10 microJ pulse at 353 nm that generates a prompt transient having a two-component decay: the first is approximately exponential with tau = 17 +/- 4 ps, whereas the second is much weaker with an approximate tau = 100 ps. At slightly lower temperature (4 degrees C), the spectrum and time dependence are essentially unchanged. In contrast to our previous observations on carboxyhemoglobin and oxyhemoglobin, we find no long-lived photoproduct in nitrosylhemoglobin. We tentatively attribute the 17 +/- 4 ps decay to geminate recombination. These results, in conjunction with our previous work in HbO2 and HbCO, show that the rate of geminate recombination for 5 ns greater than tau greater than 5 ps increases through the series HbCO less than HbO2 less than HbNO. We note that trends are also seen for microsecond recombination rates HbCO less than HbO2 approximately equal to HbNO and for the kinetic co-operativity ratio HbCO greater than HbO2 greater than HbNO. A "critical on-barrier" model is presented that provides a consistent representation of these results. We suggest that spin-orbit effects could be a major contribution to the different recombination characteristics exhibited by the three ligands.


Subject(s)
Hemoglobins , Photolysis , Carboxyhemoglobin , Kinetics , Models, Chemical , Oxyhemoglobins , Spectrum Analysis , Time Factors
5.
J Mol Biol ; 285(1): 49-54, 1999 Jan 08.
Article in English | MEDLINE | ID: mdl-9878386

ABSTRACT

We demonstrate the functional activity of single ribosomal complexes, opening the way for detailed studies of the trajectories of protein synthesis. Our approach employs a single-molecule detection system, capable of picoseconds to minutes resolution, to observe a growing peptide labeled at its N terminus with the fluorophore tetramethylrhodamine (TMR). Single complexes of mRNA-programmed ribosomes with TMR-Met-tRNAMetf or TMR-Met-Phe-tRNAPhe are immobilized on mica and observed by fluorescence. Immobilized ribosome.mRNA.TMR-Met-tRNAMetf complexes form peptide bonds with puromycin. Single-molecule detection reveals dynamics on the scale of seconds at the ribosomal peptidyl transferase center.


Subject(s)
Peptidyl Transferases/metabolism , Ribosomes/enzymology , Fluorescent Dyes , RNA, Transfer, Met/metabolism , RNA, Transfer, Phe/metabolism , Rhodamines
6.
Gene ; 163(1): 1-11, 1995 Sep 22.
Article in English | MEDLINE | ID: mdl-7557456

ABSTRACT

Combinatorial mismatch-primer mutagenesis was used to make simultaneous changes of codons for residues Trp19 and Trp99 of the Escherichia coli trp aporepressor (TrpR protein) to codons for other residues. Among 21 different single- and double-mutant repressors obtained from this round of mutagenesis, proteins with Trp-->Leu and Trp-->Met changes at one or both positions were found to be nearly as active as the wild type (wt). Genes encoding repressors with each of the eight possible combinations of single- and double-mutant changes of Trp19 and Trp99 to Leu and Met were constructed by recombination in vitro. Whereas three of these eight mutant repressors are unstable in E. coli, all are made at similar steady-state levels in Salmonella typhimurium. Three of the eight mutant holorepressors are lethal when overproduced in S. typhimurium, because they confer an induced auxotrophy. Two different activity assays in vivo show that one of the four double-mutant repressors (Trp19-->Leu; Trp99-->Met) is similar to wt TrpR in its interactions with both Trp and DNA. These results show that more general approaches to engineering active proteins with fewer Trp residues may give rise to functional mutants without aromatic substitutions, and that aliphatic changes should be considered in cases where engineered changes of Trp to Phe or Tyr do not work.


Subject(s)
Bacterial Proteins , Escherichia coli/metabolism , Repressor Proteins/biosynthesis , Tryptophan , Amino Acid Sequence , Apoproteins/biosynthesis , Base Sequence , Codon , DNA Primers , DNA, Bacterial/metabolism , Escherichia coli/genetics , Genes, Bacterial , Kinetics , Leucine , Methionine , Molecular Sequence Data , Mutagenesis, Insertional , Plasmids , Point Mutation , Promoter Regions, Genetic , Protein Engineering , Protein Structure, Secondary , Recombinant Proteins/biosynthesis , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Repressor Proteins/chemistry , Repressor Proteins/metabolism , Salmonella typhimurium/genetics , Salmonella typhimurium/metabolism
7.
Science ; 195(4273): 59-60, 1977 Jan 07.
Article in English | MEDLINE | ID: mdl-17796348
8.
Biophys Chem ; 45(2): 133-41, 1992 Dec.
Article in English | MEDLINE | ID: mdl-1286148

ABSTRACT

Fluorescence energy transfer is potentially a useful technique for obtaining structural and dynamic information on duplex and branched DNA molecules suitably labeled with donor and acceptor dyes. We have assessed the accuracy and limitations of FET measurements in nucleic acids with respect to the localization of the dyes and the flexibility of the dye-DNA linkages. A nine base-pair duplex oligonucleotide was synthesized with donor and acceptor dyes linked at the opposing 5' termini by alkyl chains. A careful analysis of the fluorescence decay of the donor revealed that the donor-acceptor distance in this molecule was not well defined, but was described by a rather broad distribution. The mean donor-acceptor distance and the distribution of distances have been recovered from the donor decay. Orientational effects on energy transfer have been included in the analysis. The implications of these findings for FET measurements in nucleic acids are considered.


Subject(s)
Coloring Agents/chemistry , DNA/chemistry , Oligonucleotides/chemistry , Base Sequence , Fluorescein , Fluoresceins/chemistry , Fluorescence Polarization , Molecular Sequence Data , Spectrometry, Fluorescence/methods
9.
J Insect Physiol ; 50(4): 259-66, 2004 Apr.
Article in English | MEDLINE | ID: mdl-15081818

ABSTRACT

Prior to this study, antifreeze proteins (AFPs) had not been identified in terrestrial arthropods from the Arctic or anywhere in Alaska. The hemolymph of 75 species of insects and six spiders from interior and arctic Alaska were screened for thermal hysteresis (a difference between the freezing and melting points), characteristic of the presence of AFPs. Eighteen species of insects and three spiders were shown to have AFPs. Ten of the insects with AFPs were beetles including the first species from the families Chrysomelidae, Pythidae, Silphidae and Carabidae. In addition, the first Neuropteran to have AFPs was identified, the lacewing Hemerobius simulans together with the second and third Diptera (the first Tipulids) and the second and third Hemiptera, the stinkbug Elasmostethus interstinctus (the first Pentatomid), and the water strider Limnoporus dissortis (the first Gerrid). Prior to this study, 33 species of insects and three spiders had been reported to have AFPs. Most AFP-producing terrestrial arthropods are freeze avoiding, and the AFPs function to prevent freezing. However, some of the AFP- producing insects identified in this study are known to be freeze tolerant (able to survive freezing) to very low temperatures (-40 to -70 degrees C).


Subject(s)
Antifreeze Proteins/metabolism , Insect Proteins/metabolism , Insecta/chemistry , Spiders/chemistry , Acclimatization/physiology , Alaska , Animals , Antifreeze Proteins/chemistry , Antifreeze Proteins/physiology , Arthropods/cytology , Arthropods/metabolism , Coleoptera/chemistry , Coleoptera/metabolism , Hemolymph/chemistry , Hemolymph/metabolism , Insect Proteins/chemistry , Insect Proteins/physiology , Insecta/metabolism , Species Specificity , Spiders/metabolism
10.
Schweiz Rundsch Med Prax ; 81(37): 1087-91, 1992 Sep 08.
Article in German | MEDLINE | ID: mdl-1455119

ABSTRACT

Manual medicine developed rapidly during the last 40 years and became an integral part of standard medicine. The basic idea behind the methods used is that several acute and chronic disorders the spine and peripheral articulations are caused by functional disturbances in one or more spinal motion segments, and also in peripheral joints, always accompanied by reflectory muscular reactions. These changes must be detected and treated specifically. The diagnosis for manual therapy is always complementary to general medical examination. Knowledge of absolute and relative contraindications is the basis for every manual therapy. Therapeutically, apart from the actual mobilization with or without impulse, the so-called neuromuscular techniques are used; these are acting together with the muscle force of the patient and with the thereby triggered reflex-mechanisms. Whereas the latter techniques are also used in physiotherapy, mobilization with impulse should be practised nowadays only by trained physicians and chiropractitioners, since the risks involved are considerable. It is of great importance that the therapy is not limited just to the manipulation of the functionally disturbed motion segment but that in addition muscular disbalance is treated.


Subject(s)
Manipulation, Orthopedic/methods , Spinal Diseases/therapy , Contraindications , Humans , Osteopathic Medicine/methods
11.
J Phys Chem A ; 110(1): 20-7, 2006 Jan 12.
Article in English | MEDLINE | ID: mdl-16392835

ABSTRACT

Fluorescent DNA-labeling cassettes are designed to have a common absorbing chromophore matched to a single exciting laser wavelength, but up to four different emitters. Experiments reported here have examined the energy-transfer rates and fluorescence polarization characteristics for two different types of cassette, involving three distinct relative orientations of the donor and acceptor transition moments and the axis of the rigid linker. Energy-transfer times range from <200 fs to approximately 20 ps, the fastest transfer times occurring when the transition moments of the donor and acceptor species are aligned parallel to the linker axis. Experimental evidence is presented that supports a through-bond energy-transfer mechanism, in contrast with a commercial DNA-labeling agent, which exhibits much slower transfer times controlled by FRET. These rigid cassettes also exhibit polarized fluorescence from the acceptor species, so that this particular type of DNA-labeling probe has some of the advantages of single-molecule probes such as rhodamine and coumarin dyes.


Subject(s)
DNA Probes/chemistry , Energy Transfer , Fluorescent Dyes/chemistry , Fluorescence Polarization , Fluorescence Resonance Energy Transfer , Molecular Structure , Time Factors
12.
Proc Natl Acad Sci U S A ; 77(6): 3110-4, 1980 Jun.
Article in English | MEDLINE | ID: mdl-16592833

ABSTRACT

An experimental and theoretical study is presented of the nonlinear response of a dilute solution being pumped by two laser fields having different frequencies omega(1) and omega(2) that are both in resonance with electronic transitions of the solute. Experimental results were obtained for the dispersion of the third-order susceptibility chi((3))(omega(2))(2) for a dilute solution of iron(III) tetraphenylporphyrin chloride in chloroform with a fixed intense field (omega(1)) resonant with the Q(o) transition and a tunable weaker field (omega(2)) resonant with the Soret transition. The observed Lorentzian dispersion is slightly narrower than the linear absorption spectrum. The theoretical model for the third-order polarization incorporates three levels coupled to two electromagnetic fields and a population reservoir. The equations of motion for the density operator were solved in third order for the appropriate Fourier component. The resulting dispersion curve depends on both total dephasing and population decay rates, thereby demonstrating a general method for the determination of subpicosecond relaxation processes in systems to which the model is applicable. Theoretical fits to the results for iron(III) tetraphenylporphyrin chloride imply that the Soret transition is essentially homogeneously broadened with a total dephasing width of 900 +/- 200 cm(-1), and it is argued that the population decay time in this case is approximately 3.5 fsec. The broad linear absorption spectrum of the Soret band is interpreted as resulting from intramolecular perturbations between the Soret and lower energy excited states of iron(III) tetraphenylporphyrin chloride.

13.
J Am Chem Soc ; 123(51): 12886-98, 2001 Dec 26.
Article in English | MEDLINE | ID: mdl-11749547

ABSTRACT

Molecular dynamics simulations of the structural distributions and the associated amide-I vibrational modes are carried out for dialanine peptide in water and carbon tetrachloride. The various manifestations in nonlinear-infrared spectroscopic experiments of the distributions of conformations of solvated dialanine are examined. The two-dimensional infrared (2D-IR) spectrum of dialanine exhibits the coupling between the amide oscillators and the correlations of the frequency fluctuations. An internally hydrogen-bonded conformation exists in CCl(4) but not in H(2)O where two externally hydrogen-bonded forms are preferred. Simulations of solvated dialanine show how the 2D-IR spectra expose the underlying structural distributions and dynamics that are not deducible from linear-infrared spectra. In H(2)O the 2D-IR shows cross-peaks from large coupling in the alpha-helical conformer and an elongated higher frequency diagonal peak, reflecting the broader distribution of structures for the more flexible acetyl end. In CCl(4), the computed cross-peak portion of the 2D-IR shows evidence of two amide-I transitions in the high-frequency region which are not apparent from the diagonal peak profile. The vibrational frequency inhomogeneity of the amide-I band arises from fluctuations of the instantaneous normal modes of these conformers rather than the shifts induced by hydrogen bonding. The simulation shows that there are correlations between fluctuations of the acetyl and amino end frequencies in H(2)O that arise from mechanical coupling and not from hydrogen bonding at the two ends of the molecule. The angular relationships between the two amide units which also show up in 2D-IR were computed, and spectral manifestations of them are discussed. The simulations also permit a calculation of the rate of energy transfer from one side of the molecule to the other. From these calculations, 2D-IR spectroscopy in conjunction with simulations is seen to be a promising tool for determining dynamics of structure changes in dipeptides.


Subject(s)
Dipeptides/chemistry , Spectrophotometry, Infrared/methods , Models, Chemical , Protein Conformation , Protein Structure, Secondary , Thermodynamics , Vibration
14.
Proc Natl Acad Sci U S A ; 84(17): 6142-6, 1987 Sep.
Article in English | MEDLINE | ID: mdl-3476936

ABSTRACT

The fluorescence of heme proteins is influenced by energy transfer from the excited tryptophan to the heme. Molecular dynamics simulations of the tryptophan and heme motions in sperm whale myoglobin were used to calculate the fluorescence intensity and anisotropy decays. The side chains underwent both small rapid orientational fluctuations and large infrequent transitions between conformations. The predicted motions of the tryptophans and the heme produce large fluctuations in the instantaneous rate of energy transfer, but no stable conformations in which energy transfer is suppressed were found. The calculated fluorescence anisotropies exhibited a large subpicosecond decay, corresponding to nondiffusive side-chain motions. The calculations adequately predict the observed fluorescence decay curve for myoglobin and the total anisotropy decay at 16-ps time resolution. The subnanosecond decays of anisotropy for tryptophan-14 in tuna myoglobin are not reproduced by the calculation.


Subject(s)
Hemeproteins , Metmyoglobin , Tryptophan , Animals , Fluorescence Polarization , Heme , Models, Chemical , Protein Conformation , Thermodynamics , Whales
15.
Opt Lett ; 25(16): 1210-2, 2000 Aug 15.
Article in English | MEDLINE | ID: mdl-18066171

ABSTRACT

We describe a new four-wave rectification method for the generation of intense, ultrafast terahertz (THz) pulses from gases. The fundamental and second-harmonic output of an amplified Ti:sapphire laser is focused to a peak intensity of ~5x10(14)W/cm (2) . Under these conditions, peak THz fields estimated at 2 kV/cm have been observed; the measured power spectrum peaks near 2 THz. Phase-dependent measurements show that this is a coherent process and is sensitive to the relative phases of the fundamental and second-harmonic pulses. Comparable THz signals have been observed from nitrogen and argon as well as from air.

16.
Proc Natl Acad Sci U S A ; 81(14): 4399-403, 1984 Jul.
Article in English | MEDLINE | ID: mdl-6589602

ABSTRACT

The fluorescence decay characteristics of Mb, MbCO, metMb (sperm whale), metMb (yellowfin tuna), and their apo derivatives were determined by using a picosecond streak camera and time-correlated single photon counting. The emission is dominated by tryptophans that transfer their energy to the heme on a subnanosecond time scale. Sperm whale Mb and derivatives have two tryptophans and their decays can be interpreted mainly as two exponentials, one of ca. 20 ps and the other of 130 ps, whereas tuna Mb has one tryptophan and its emission is nonexponential but dominated by one component of 31 ps. These results along with Förster energy transfer calculations allow us to assign the ca. 30-ps emission to Trp-14 and the 130-ps emission to Trp-7 in Mb. The streak camera was modified to determine the decay of the fluorescence anisotropy. In metMb (tuna) the fluorescence anisotropy decays in 100 ps, which is postulated to result from rapid motion of the Trp-14. Because energy transfer was used to gate the anisotropy, the fast motion of Trp-14 is proposed to correspond to only 10% of the equilibrium distribution of molecules.


Subject(s)
Apoproteins , Myoglobin , Tryptophan , Animals , Energy Transfer , Fluorescence Polarization , Heme , Mathematics , Metmyoglobin , Time Factors , Tuna , Whales
17.
Biophys J ; 60(1): 286-9, 1991 Jul.
Article in English | MEDLINE | ID: mdl-1883942

ABSTRACT

Picosecond infrared spectroscopy is developed and used for the first time to study the dynamics of photoexcited bacteriorhodopsin (BR). Both spectral and time-resolved data are obtained. The results open an entirely new approach to investigations of the BR photocycle. The infrared difference spectrum (K minus BR570) recorded at ambient temperature between 1,560 and 1,700 cm-1 is not identical with the spectrum reported for a frozen sample. Three bands of the K state at 1,622, 1,610, and 1,580 cm-1 and the bleaching at 1,637 cm-1 (C = NH stretch) are seen. These new spectral lines appear in less than 10 ps.


Subject(s)
Bacteriorhodopsins/chemistry , Bacteriorhodopsins/metabolism , Kinetics , Protein Conformation , Spectrophotometry, Infrared/instrumentation , Spectrophotometry, Infrared/methods , Thermodynamics
18.
Proc Natl Acad Sci U S A ; 92(16): 7292-6, 1995 Aug 01.
Article in English | MEDLINE | ID: mdl-7638183

ABSTRACT

A temperature jump (T-jump) method capable of initiating thermally induced processes on the picosecond time scale in aqueous solutions is introduced. Protein solutions are heated by energy from a laser pulse that is absorbed by homogeneously dispersed molecules of the dye crystal violet. These act as transducers by releasing the energy as heat to cause a T-jump of up to 10 K with a time resolution of 70 ps. The method was applied to the unfolding of RNase A. At pH 5.7 and 59 degrees C, a T-jump of 3-6 K induced unfolding which was detected by picosecond transient infrared spectroscopy of the amide I region between 1600 and 1700 cm-1. The difference spectral profile at 3.5 ns closely resembled that found for the equilibrium (native-unfolded) states. The signal at 1633 cm-1, corresponding to the beta-sheet structure, achieved 15 +/- 2% of the decrease found at equilibrium, within 5.5 ns. However, no decrease in absorbance was detected until 1 ns after the T-ump. The disruption of beta-sheet therefore appears to be subject to a delay of approximately 1 ns. Prior to 1 ns after the T-jump, water might be accessing the intact hydrophobic regions.


Subject(s)
Ribonuclease, Pancreatic/chemistry , Animals , Cattle , Hot Temperature , Hydrogen Bonding , In Vitro Techniques , Kinetics , Molecular Structure , Pancreas/enzymology , Protein Folding , Protein Structure, Secondary , Solutions , Spectroscopy, Fourier Transform Infrared , Thermodynamics , Water
19.
Opt Lett ; 19(12): 895-7, 1994 Jun 15.
Article in English | MEDLINE | ID: mdl-19844480

ABSTRACT

18-fs pulses from a self-mode-locked Ti:sapphire laser are amplified to 60 microJ of energy at 4.9 kHz with chirped-pulse amplification in a Ti:sapphire regenerative amplifier. After recompression, 30-35-fs, near-transform-limited pulses are obtained.

20.
Proc Natl Acad Sci U S A ; 91(22): 10670-4, 1994 Oct 25.
Article in English | MEDLINE | ID: mdl-7938011

ABSTRACT

Fluorescence depolarization decays were measured for 5-dimethylaminonaphthalene-1-sulfonyl (dansyl) probes attached internally to 17-mer.27-mer oligonucleotides bound to Klenow fragment of DNA polymerase I. The time-resolved motions of the dansyl probes were sensitive indicators of DNA-protein contacts, showing that the protein binds to DNA with two footprints, corresponding to primer termini at either the polymerase or 3'-5' exonuclease sites. We examined complexes of Klenow fragment with DNAs containing various base mismatches. Single mismatches at the primer terminus caused a 3- to 4-fold increase in the equilibrium partitioning of DNA into the exonuclease site; the largest effects were observed for purine-purine mismatches. Two or more consecutive G.G mismatches caused the DNA to bind exclusively at the exonuclease site, with a partitioning constant at least 250-fold greater than that of the corresponding matched DNA sequence. Internal single mismatches produced larger effects than the same mismatch at the primer terminus, with a delta delta G relative to the matched sequence of -1.1 to -1.3 kcal/mol for mismatches located 2, 3, or 4 bases from the primer terminus. Although part of the observed effects may be attributed to the increased melting capacity of the DNA, it appears that the polymerase site also promotes movement of DNA into the exonuclease site by rejecting aberrant primer termini. These effects suggest that the polymerase and exonuclease sites act together to recognize specific errors that distort the primer terminus, such as frameshifts, in addition to proofreading misincorporated bases.


Subject(s)
DNA Polymerase I/metabolism , DNA/chemistry , DNA/metabolism , Nucleic Acid Conformation , Base Sequence , Binding Sites , Calorimetry , DNA Primers , Dansyl Compounds , Fluorescence Polarization , Kinetics , Mathematics , Models, Structural , Molecular Sequence Data
SELECTION OF CITATIONS
SEARCH DETAIL