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1.
Artigo em Inglês | MEDLINE | ID: mdl-39020128

RESUMO

PURPOSE: In pertrochanteric femur fractures the risk for fracture healing complications increases with the complexity of the fracture. In addition to dynamization along the lag screw, successful fracture healing may also be facilitated by further dynamization along the shaft axis. The aim of this study was to investigate the mechanical stability of additional axial notch dynamization compared to the standard treatment in an unstable pertrochanteric femur fracture treated with cephalomedullary nailing. METHODS: In 14 human cadaver femora, an unstable pertrochanteric fracture was stabilized with a cephalomedullary nail. Additional axial notch dynamization was enabled in half of the samples and compared against the standard treatment (n = 7). Interfragmentary motion, axial construct stiffness and load to failure were investigated in a stepwise increasing cyclic load protocol. RESULTS: Mean load to failure (1414 ± 234 N vs. 1428 ± 149 N, p = 0.89) and mean cycles to failure (197,129 ± 45,087 vs. 191,708 ± 30,490, p = 0.81) were equivalent for axial notch dynamization and standard treatment, respectively. Initial construct stiffness was comparable for both groups (axial notch dynamization 684 [593-775] N/mm, standard treatment 618 [497-740] N/mm, p = 0.44). In six out of seven specimens the additional axial dynamization facilitated interfragmentary compression, while maintaining its mechanical stability. After initial settling of the constructs, there were no statistically significant differences between the groups for either subsidence or rotation of the femoral head fragment (p ≤ 0.30). CONCLUSION: Axial notch dynamization provided equivalent mechanical stability compared to standard treatment in an unstable pertrochanteric fracture. Whether the interfragmentary compression generated by axial notch dynamization will promote fracture healing through improved fracture reduction needs to be evaluated clinically.

2.
Chemistry ; : e202402055, 2024 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-38884181

RESUMO

Enzymes play a fundamental role in cellular metabolism. A wide range of enzymes require the presence of complementary coenzymes and cofactors to function properly. While coenzymes are believed to have been part of the last universal ancestor (LUCA) or have been present even earlier, the syntheses of crucial coenzymes like the redox-active coenzymes flavin adenine dinucleotide (FAD) or nicotinamide adenine dinucleotide (NAD+) remain challenging. Here, we present a pathway to NAD+ under prebiotic conditions starting with ammonia, cyanoacetaldehyde, prop-2-ynal and sugar-forming precursors, yielding in situ the nicotinamide riboside. Regioselective phosphorylation and water stable light activated adenosine monophosphate derivatives allow for topographically and irradiation-controlled formation of NAD+. Our findings indicate that NAD+, a coenzyme vital to life, can be formed non-enzymatically from simple organic feedstock molecules via photocatalytic activation under prebiotically plausible early Earth conditions in a continuous process under aqueous conditions.

3.
Nat Commun ; 13(1): 6488, 2022 10 30.
Artigo em Inglês | MEDLINE | ID: mdl-36310176

RESUMO

α-Amanitin is a bicyclic octapeptide composed of a macrolactam with a tryptathionine cross-link forming a handle. Previously, the occurrence of isomers of amanitin, termed atropisomers has been postulated. Although the total synthesis of α-amanitin has been accomplished this aspect still remains unsolved. We perform the synthesis of amanitin analogs, accompanied by in-depth spectroscopic, crystallographic and molecular dynamics studies. The data unambiguously confirms the synthesis of two amatoxin-type isomers, for which we propose the term ansamers. The natural structure of the P-ansamer can be ansa-selectively synthesized using an optimized synthetic strategy. We believe that the here described terminology does also have implications for many other peptide structures, e.g. norbornapeptides, lasso peptides, tryptorubins and others, and helps to unambiguously describe conformational isomerism of cyclic peptides.


Assuntos
Alfa-Amanitina , Peptídeos Cíclicos , Alfa-Amanitina/química , Amanitinas/química , Isomerismo , Peptídeos
4.
Chirality ; 34(5): 732-759, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35315953

RESUMO

Chiral compounds are ubiquitous in nature and play a pivotal role in biochemical processes, in chiroptical materials and applications, and as chiral drugs. The analysis and determination of the enantiomeric ratio (er) of chiral compounds is of enormous scientific, industrial, and economic importance. Chiral separation techniques and methods have become indispensable tools to separate chiral compounds into their enantiomers on an analytical as well on a preparative level to obtain enantiopure compounds. Chiral gas chromatography and high-performance liquid chromatography have paved the way and fostered several research areas, that is, asymmetric synthesis and catalysis in organic, medicinal, pharmaceutical, and supramolecular chemistry. The development of highly enantioselective chiral stationary phases was essential. In particular, the elucidation and understanding of the underlying enantioselective supramolecular separation mechanisms led to the design of new chiral stationary phases. This review article focuses on the development of chiral stationary phases for gas chromatography. The fundamental mechanisms of the recognition and separation of enantiomers and the selectors and chiral stationary phases used in chiral gas chromatography are presented. An overview over syntheses and applications of these chiral stationary phases is presented as a practical guidance for enantioselective separation of chiral compound classes and substances by gas chromatography.


Assuntos
Estereoisomerismo , Cromatografia Gasosa , Cromatografia Líquida de Alta Pressão
5.
Nat Commun ; 12(1): 7182, 2021 12 10.
Artigo em Inglês | MEDLINE | ID: mdl-34893619

RESUMO

The formation of peptide bonds is one of the most important biochemical reaction steps. Without the development of structurally and catalytically active polymers, there would be no life on our planet. However, the formation of large, complex oligomer systems is prevented by the high thermodynamic barrier of peptide condensation in aqueous solution. Liquid sulphur dioxide proves to be a superior alternative for copper-catalyzed peptide condensations. Compared to water, amino acids are activated in sulphur dioxide, leading to the incorporation of all 20 proteinogenic amino acids into proteins. Strikingly, even extremely low initial reactant concentrations of only 50 mM are sufficient for extensive peptide formation, yielding up to 2.9% of dialanine in 7 days. The reactions carried out at room temperature and the successful use of the Hadean mineral covellite (CuS) as a catalyst, suggest a volcanic environment for the formation of the peptide world on early Earth.


Assuntos
Aminoácidos/química , Planeta Terra , Origem da Vida , Peptídeos/química , Dióxido de Enxofre/química , Catálise , Cobre/química , Dipeptídeos , Minerais/química , Água
6.
Electrophoresis ; 41(15): 1280-1286, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32358866

RESUMO

The hyphenation of capillary electrophoresis with high-resolution mass spectrometry, such as Orbitrap MS, is of broad interest for the unambiguous and exceptionally sensitive identification of compounds. However, the coupling of these techniques requires a robust ionization interface that does not influence the stability of the separation voltage while coping with oxidation of the emitter tip at large ionization voltages. Herein, we present the design of a sheath-flow CE-ESI-MS interface which combines a robust and easy to operate set-up with high-resolution Orbitrap MS detection. The sheath liquid interface is equipped with a gold coated electrospray emitter which increases the stability and overall lifetime of the system. For the characterization of the interface, the spray stability and durability were investigated in dependence of the sheath-flow rate, electrospray voltage, and additional gold coating. The optimized conditions were applied to a separation of angiotensin II and neurotensin resulting in LODs of 2.4 and 3.5 ng/mL.


Assuntos
Eletroforese Capilar/métodos , Espectrometria de Massas por Ionização por Electrospray/métodos , Limite de Detecção , Peptídeos/análise , Peptídeos/isolamento & purificação , Reprodutibilidade dos Testes
7.
Injury ; 51 Suppl 2: S51-S56, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31706585

RESUMO

Intraoperative imaging has been advanced substantially over the last decades. It supports localization of the region of interest, verification of the preoperatively classified fracture pattern, identification of correct insertion point of the implant, placement of instruments and fixation material, and verification of correct fracture reduction and implant positioning. While conventional fluoroscopic 2D imaging remains the gold standard in intraoperative imaging, critical anatomical regions are predestined for intraoperative 3D imaging. Additional options such as perioperative virtual planning, simulation, and surgical training, 3D printing techniques and 3D augmented reality visualization may potentially open new windows to improve surgical results in fracture care. This manuscript presents an update on current and upcoming imaging techniques in orthopaedic and trauma surgery focusing on technical advances for decreasing malreduction, malalignment, and malposition, as well as tips and tricks for daily surgical practice in order to improve clinical outcomes and patients' and surgeons' safety.


Assuntos
Fluoroscopia/métodos , Fixação Interna de Fraturas/métodos , Fraturas Ósseas/cirurgia , Imageamento Tridimensional , Impressão Tridimensional , Fraturas Ósseas/diagnóstico por imagem , Humanos , Monitorização Intraoperatória/instrumentação , Monitorização Intraoperatória/métodos , Cirurgia Assistida por Computador
8.
Anal Chim Acta ; 1081: 200-208, 2019 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-31446959

RESUMO

This study develops analytical approaches using comprehensive heart-cut multidimensional gas chromatography (H/C MDGC) to experimentally investigate effects of concentration and temperature on peak shapes and on kinetic analysis of E/Z isomerisation of oximes which undergo various extents of interconversion on 1D and 2D separation columns. Different stationary phase combinations were investigated. An SLB-IL76 1D column results in good separation of the isomers but with negligible interconversion (1Dsep). Precise targeted heart-cuts (H/C; 3-15 s windows) and cryogenic trapping of selected sections eluting from this 1D column allows well controlled E/Z isomer ratios to be delivered to a 2D poly(ethyleneglycol) (PEG) phase column. This phase catalyses oxime interconversion, with separation; this is termed 2Dinter. This column set describes a 1Dsep × 2Dinter arrangement. The interconversion forward rate constant (k1UE, calculated by using DCXplorer) was found to be independent of the %E isomer (i.e. first order kinetics); k1UE increased at higher temperature (increased Gibbs activation energies, ΔGapp). In addition, a long 1D SLB-IL111 column gave oxime separation with interconversion (1Dinter). Comprehensive multiple H/C of the zone performed on the 2D PEG (2Dinter) at 40, 60 and 80 °C resulted in a 2D presentation (1Dinter × 2Dinter) with a unique rectangular display of interconversion from each H/C pulse with varied isomer concentration ratios. Data for k1UE from 1DGC analysis suggests underestimation of k1UE on 1Dinter SLB-IL111 from the 2D result. The k1UE value on 2Dinter PEG column is more reliably evaluated by summation of all the 2Dinter profiles rather than that obtained from the average value for the individual H/C pulses.

9.
J Chromatogr A ; 1595: 180-189, 2019 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-30803787

RESUMO

The development of fast and precise measurement techniques for process analytical technology is important to operate chemical processes safely and efficiently. For quantitative measurements of multiple components at a trace level, often gas chromatographic methods are used which have a response time of several minutes or of up to one hour. For fast changing processes, this can be too slow for efficient control. For reducing the dead time of a control loop by increasing the measurement frequency, a multiplexing gas chromatography (mpGC) technique for a chromatographic system exhibiting a systematic non-linear response has been developed. For mpGC, superimposed chromatograms are measured by injecting consecutive samples before all components of previous samples have eluted from the column. The deconvolution of a superimposed chromatogram yields a computed chromatogram which is an average over the single chromatograms forming the superimposed chromatogram. Such a computed chromatogram typically shows so called correlation noise depending on the degree by which the single chromatograms forming the superimposed chromatogram will differ from each other (non-linear response). A technique is presented to calibrate the convolution matrix in order to suppress correlation noise introduced by systematic errors of the chromatographic system. The remaining correlation noise in the computed chromatogram is then exclusively caused by changing concentrations in the sample stream. For the method presented here, the sample is injected five times during the run time of a single chromatogram. The computed chromatogram is obtained three times within this timespan while representing each time an averaged chromatogram over the last five injections. Therefore, the sample throughput is increased by a factor of three compared to conventional GC.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Gasosa , Calibragem
10.
J Am Chem Soc ; 141(1): 334-341, 2019 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-30525577

RESUMO

Formaldehyde is an important precursor to numerous industrial processes and is produced in multimillion ton scale every year by catalytic oxidation of methanol in an energetically unfavorable and atom-inefficient industrial process. In this work, we present a highly selective one-step synthesis of a formaldehyde derivative starting from carbon dioxide and hydrogen gas utilizing a homogeneous ruthenium catalyst. Here, formaldehyde is obtained as dimethoxymethane, its dimethyl acetal, by selective reduction of carbon dioxide at moderate temperatures (90 °C) and partial pressures (90 bar H2/20 bar CO2) in the presence of methanol. Besides the desired product, only methyl formate is formed, which can be transformed to dimethoxymethane in a consecutive catalytic step. By comprehensive screening of the catalytic system, maximum turnover numbers of 786 for dimethoxymethane and 1290 for methyl formate were achieved with remarkable selectivities of over 90% for dimethoxymethane.

11.
J Chromatogr A ; 1568: 160-167, 2018 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-30122163

RESUMO

The separation and analysis of complex monosaccharide mixtures is highly challenging and requires typically carefully selected derivatization procedures to avoid changes in the sample composition. Here we present in a comparative study several single- and two-step derivatization approaches for LC and GC separations using a set of reference compounds ranging from C1 building block such as formaldehyde to C6 monosaccharides. Separation conditions have been optimized resulting in the simultaneous separation of 15 unbranched aldoses. By parallel derivatization using hydroxylamine hydrochloride (HACl)/ N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and O-ethylhydroxylamine hydrochloride (EtOx)/ N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and comparative GC measurements we developed a protocol for the unambiguous identification and separation of aldoses, ketoses, alditols and aldonic acids, which commonly occur in complex sugar mixtures as reaction by-products or decomposition products. In particular this procedure helps to deconvolute overlapping analytes and facilitates quantification. Additionally, the method presented here has been investigated in regard to storage life, detection limits, quantification and MS analysis. The broad applicability of this method to different sample matrices is shown for the analysis of food samples and complex aldol reaction mixtures in the formose reaction, which is of great relevance in the context of the origin of life.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Monossacarídeos/análise , Carboidratos/química , Misturas Complexas , Alimentos , Limite de Detecção , Monossacarídeos/química , Compostos de Trimetilsilil/química
12.
Anal Chem ; 90(15): 9256-9263, 2018 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-30001483

RESUMO

Developing new catalysts is crucial for optimization of chemical processes. Thus, advanced analytical methods are required to determine the catalytic performance of new catalysts accurately. Usually, gas chromatographic methods are employed to analyze quantitatively the product distribution of volatile compounds generated by a specific catalyst. However, the characterization of rapidly changing catalysts, e.g., due to deactivation, still poses an analytical challenge because gas chromatographic methods are too slow for monitoring the change of the complex product spectra. Here, we developed a gas chromatographic technique based on the concept of multiplexing gas chromatography (mpGC) for fast and comprehensive analysis of the product stream from a catalytic testing unit. This technique is applied for the study of the catalytic reaction of methanol-to-olefins (MTO) conversion. For this method, the time distance between two measurements is chosen so that the chromatograms but not the peaks themselves are superimposed. In this way, stacked chromatograms are generated in which the components from successively injected samples elute baseline separated next to each other from the column. The peaks from different samples are interlaced, and for this reason, the method is referred to as time-division multiplexing gas chromatography (td-mpGC). The peaks are analyzed by direct peak integration not requiring a Hadamard transformation for deconvolution of the raw data as usual for many mpGC applications. Therefore, the sample can be injected equidistantly. The integrated peaks have to be allocated to the correct retention times. The time distance between two measurements for studying the reaction and regeneration cycles of MTO catalysts is 4.3 min and 38 s, respectively. Column switching techniques such as back-flush and heart-cut are introduced as general tools for multiplexing gas chromatography.

13.
Plant J ; 91(4): 725-740, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28509359

RESUMO

Multiple pathways exist to repair DNA damage induced by methylating and crosslinking agents in Arabidopsis thaliana. The SWI2/SNF2 translocase RAD5A, the functional homolog of budding yeast Rad5 that is required for the error-free branch of post-replicative repair, plays a surprisingly prominent role in the repair of both kinds of lesions in Arabidopsis. Here we show that both the ATPase domain and the ubiquitination function of the RING domain of the Arabidopsis protein are essential for the cellular response to different forms of DNA damage. To define the exact role of RAD5A within the complex network of DNA repair pathways, we crossed the rad5a mutant line with mutants of different known repair factors of Arabidopsis. We had previously shown that RAD5A acts independently of two main pathways of replication-associated DNA repair defined by the helicase RECQ4A and the endonuclease MUS81. The enhanced sensitivity of all double mutants tested in this study indicates that the repair of damaged DNA by RAD5A also occurs independently of nucleotide excision repair (AtRAD1), single-strand break repair (AtPARP1), as well as microhomology-mediated double-strand break repair (AtTEB). Moreover, RAD5A can partially complement for a deficient AtATM-mediated DNA damage response in plants, as the double mutant shows phenotypic growth defects.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Reparo do DNA , Adenosina Trifosfatases/genética , Adenosina Trifosfatases/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Dano ao DNA , DNA Helicases/genética , DNA Helicases/metabolismo , Domínios Proteicos , Ubiquitinação
14.
Anal Chem ; 89(7): 4038-4045, 2017 04 04.
Artigo em Inglês | MEDLINE | ID: mdl-28274122

RESUMO

The analysis of impurities at a trace level in chemical products, nutrition additives, and drugs is highly important to guarantee safe products suitable for consumption. However, trace analysis in the presence of a dominating component can be a challenging task because of noncompatible linear detection ranges or strong signal overlap that suppresses the signal of interest. Here, we developed a technique for quantitative analysis using multiplexing gas chromatography (mpGC) for continuous and completely automated process trace analytics exemplified for the analysis of a CO2 stream in a production plant for detection of benzene, toluene, ethylbenzene, and the three structural isomers of xylene (BTEX) in the concentration range of 0-10 ppb. Additional minor components are methane and methanol with concentrations up to 100 ppm. The sample is injected up to 512 times according to a pseudorandom binary sequence (PRBS) with a mean frequency of 0.1 Hz into a gas chromatograph equipped with a flame ionization detector (FID). A superimposed chromatogram is recorded which is deconvoluted into an averaged chromatogram with Hadamard transformation. Novel algorithms to maintain the data acquisition rate of the detector by application of Hadamard transformation and to suppress correlation noise induced by components with much higher concentrations than the target substances are shown. Compared to conventional GC-FID, the signal-to-noise ratio has been increased by a factor of 10 with mpGC-FID. Correspondingly, the detection limits for BTEX in CO2 have been lowered from 10 to 1 ppb each. This has been achieved despite the presence of detectable components (methane and methanol) with a concentration about 1000 times higher than the target substances. The robustness and reliability of mpGC has been proven in a two-month field test in a chemical production plant.

15.
Arch Orthop Trauma Surg ; 135(2): 179-185, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25466724

RESUMO

INTRODUCTION: Mechanical breakage of cephalomedullary nail osteosynthesis is a rare complication attributed to delayed fracture union or nonunion. This study presents a series of cases of breakage and secondary lag screw dislocation after cephalomedullary nailing. The aim of this study was to identify factors that contribute to cephalomedullary nail breakage. MATERIALS AND METHODS: In a retrospective case series review between 02/2005 and 12/2013, we analyzed 453 patients with trochanteric and subtrochanteric fracture who had been treated by cephalomedullary nailing. Fractures were classified according to AO/OTA classification. 13 patients with cephalomedullary nail breakage were included (failure rate 2.9 %). RESULTS: Seven patients were women, and six men with a mean age of 72 years (range 35-94). Implant breakage occurred 6 months postoperatively (range 1-19 months). In ten cases, breakage was secondary to delayed or nonunion, which was thought to be mainly due to insufficient reduction of the fracture, and in two cases due to loss of the lag screw because of missing set screw. In one case, breakage was apparent during elective metal removal following complete fracture healing. Short-term outcome was evaluated 6 months after operative revision using Harris hip score in 11 out of 13 patients showing a mean score of 84 %. Complete radiological fracture healing has been found in 11 patients available for follow-up within 6 months after revision surgery. DISCUSSION: Breakage of cephalomedullary nail osteosynthesis of trochanteric fractures is a severe complication. The results of our study demonstrate that revision surgery provides good clinical and radiological short-term results. Predominately, failures of trochanteric fractures are related to lack of surgeon performance. Therefore, application of the implant requires accurate preoperative planning, advanced surgical experience to evaluate the patient and the fracture classification, and precise surgical technique including attention to detail and anatomical reduction of the fracture fragments.


Assuntos
Fixação Intramedular de Fraturas/efeitos adversos , Fraturas do Quadril/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Pinos Ortopédicos/efeitos adversos , Parafusos Ósseos/efeitos adversos , Feminino , Fixação Intramedular de Fraturas/instrumentação , Consolidação da Fratura , Fraturas Mal-Unidas/etiologia , Fraturas Mal-Unidas/cirurgia , Fraturas não Consolidadas/etiologia , Fraturas não Consolidadas/cirurgia , Fraturas do Quadril/complicações , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
16.
Electrophoresis ; 36(5): 796-804, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25502411

RESUMO

The phthalimidone derivatives EM12 and lenalidomide, which are both structurally related to thalidomide, are highly interesting drugs and very recently lenalidomide attracted great attention as an antitumor and immune-modulating drug in the therapy for multiple myeloma. EM12 and lenalidomide are chiral, and the stereogenic carbon C-3 in the piperidine-2,6-dione moiety of these phthalimidone derivatives is prone to interconversion due to keto-enol tautomerization. The knowledge of the enantiomerization barrier is mandatory for pharmacokinetic studies and to develop a tailored therapy using the enantiopure or racemic drug. Here, we used dynamic EKC in combination with direct-calculation methods to determine the enantiomerization barriers of EM12 and lenalidomide. The separations of the enantiomers of EM12 and lenalidomide were performed in 50 mM aqueous disodium hydrogen phosphate buffer at pH 8 and 50 mM aqueous sodium tetraborate buffer at pH 9.3, respectively, using 20 mg/mL heptakis-(2,3-diacetyl-6-sulfato)-ß-CD as a chiral additive. Enantiomerization of the compounds during the electrokinetic chromatographic separation resulted in pronounced plateau formation between the well-separated enantiomers. Peak form analysis of the experimentally obtained interconversion profiles yielded the enantiomerization rate constants k1 of EM12 and lenalidomide as well as the kinetic activation parameters ΔG(‡), ΔH(‡‡), and ΔS(‡) of enantiomerization by the evaluation of temperature-dependent measurements. The enantiomerization barrier ΔG(‡) was determined to be 98.3 ± 1.0 kJ/mol; the activation parameters ΔH(‡) = 46.1 ± 2.4 kJ/mol and ΔS(‡) = -170 ± 61 J/(K·mol) for EM12 and ΔG(‡) = 91.5 ± 1.0 kJ/mol, ΔH(‡) = 62.4 ± 5.4 kJ/mol, and ΔS(‡) = -98 ± 7 J/(K·mol) for lenalidomide. These findings were corroborated by density functional theory calculations at the B3LYP/3-21G level of theory of the ground state and intermediates considering an enantiomerization pathway via a keto-enol tautomerism.


Assuntos
Antineoplásicos/química , Cromatografia Capilar Eletrocinética Micelar/métodos , Talidomida/análogos & derivados , Talidomida/química , Lenalidomida , Modelos Moleculares , Estereoisomerismo , Termodinâmica
17.
Angew Chem Int Ed Engl ; 53(15): 3835-9, 2014 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-24595963

RESUMO

A novel UV-initiated surface modification method for the direct functionalization of surface hydroxy groups with thiol-containing molecules (termed "thiol-ol" modification) is described. This method is based on the oxidative conjugation of thiols to hydroxy groups. We demonstrate that different thiol-containing molecules, such as fluorophores, thiol-terminated poly(ethylene glycol) (PEG-SH), and a cysteine-containing peptide, can be attached onto the surface of porous poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate). Direct functionalization of other hydroxy-group-bearing surfaces, fabrication of micropatterns, and double patterning have been also demonstrated using the thiol-ol method.

18.
Science ; 342(6162): 1084-6, 2013 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-24288330

RESUMO

In chemistry and biology, chirality, or handedness, refers to molecules that exist in two spatial configurations that are incongruent mirror images of one another. Almost all biologically active molecules are chiral, and the correct determination of their absolute configuration is essential for the understanding and the development of processes involving chiral molecules. Anomalous x-ray diffraction and vibrational optical activity measurements are broadly used to determine absolute configurations of solid or liquid samples. Determining absolute configurations of chiral molecules in the gas phase is still a formidable challenge. Here we demonstrate the determination of the absolute configuration of isotopically labeled (R,R)-2,3-dideuterooxirane by foil-induced Coulomb explosion imaging of individual molecules. Our technique provides unambiguous and direct access to the absolute configuration of small gas-phase species, including ions and molecular fragments.


Assuntos
Óxido de Etileno/química , Imagem Molecular/métodos , Deutério , Fenômenos Eletromagnéticos , Gases , Marcação por Isótopo , Conformação Molecular , Estereoisomerismo
19.
J Chromatogr A ; 1269: 346-51, 2012 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-22909893

RESUMO

Novel 3-(perfluoroalkanoyl)-(1R)-camphorate nickel complexes immobilized to poly(dimethylsiloxane) phases are presented. Immobilized 3-(perfluoroalkanoyl)-(1R)-camphorate nickel complexes with a trifluoromethyl (CF(3); nickel(II)-bis[(1R,4S)-3-trifluoromethanoyl-10-propylenoxycamphor]-polysiloxane Ni(tfpc)(2)@PS) and a heptafluoropropyl-substituent (C(3)F(7); nickel(II)-bis[(1R,4S)-3-heptafluorobutanoyl-10-propylenoxycamphor]-polysiloxane Ni(hfpc)(2)@PS) were synthesized, characterized and immobilized to polysiloxane. Ni(hfpc)(2)@PS was immobilized with a selector content of 38% and their enantioseparation ability was compared to selector concentrations of 4% and 20%. The influence of the perfluorinated moiety as well as the effect of the selector concentration on enantioseparations were investigated. Based on different functionalized organic compounds the quality of enantioseparation was analyzed and compared.


Assuntos
Cânfora/química , Cromatografia Gasosa/métodos , Níquel/química , Cânfora/análogos & derivados , Espectroscopia de Ressonância Magnética , Espectroscopia de Infravermelho com Transformada de Fourier , Estereoisomerismo
20.
Foot Ankle Surg ; 17(4): 277-83, 2011 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22017903

RESUMO

BACKGROUND: Regardless of the simple surgical technique, the success of the subtalar arthrodesis is limited by the rate of non-unions of the arthrodesis. The functional outcome of workers compensation is known to be poorer compared to patients without pending litigation. The aim of this study was to quantify the rate of non-unions and to determine risk factors leading to failure of the osseous consolidation after arthrodesis of the subtalar joint. The outcome assessed is a general health assessment with the SF-36 questionnaire and more illness specific with the AOFAS hindfoot score. Secondly, the influence of the health insurance status of the patients with or without worker's compensation on the outcome was tested. METHODS AND RESULTS: The inclusive criterion was an arthrodesis of the subtalar joint with and without autologous cancellous bone grafting and screw osteosynthesis. This cohort study included the clinical course of 115 patients with posttraumatic osteoarthritis from 2000 to 2006. The average age of the patients (n=115) was 47±11.0 years, 83% of the treated patients were men. 68% of the patients suffered of secondary osteoarthritis after calcaneal fracture. The time interval from trauma to presenting at the physician due to therapy resistant pain was in the average 5.5±9.9 years. After primary arthrodesis (n=101) of the subtalar joint osseous consolidation was proved in 55% cases, consolidation was questionable in 21% and the rate of no consolidation with revision was remarkable high with 24%. The duration of osseous consolidation was proved by plain projection radiography or computer tomography and clinical reduction of pain. For primary arthrodesis osseous consolidation was reached after 6.4±6.3 month, after secondary arthrodesis osseous consolidation was reached after 9.4±13.1 month. After revision surgery 57% of the arthrodesis healed, 12% the osseous consolidation was questionable, and the failure rate was still 12%. CONCLUSION: The outcome measures of the patients with SF-36 and the more functional related AOFAS hindfoot score showed poor outcome rates after subtalar fusion in posttraumatic osteoarthritis. The AOFAS hindfoot score was 47±24 points after primary arthrodesis and 46±17 points after secondary arthrodesis of the subtalar joint. The patients regained their former ability to work only in 30% after fusion of the subtalar joint. If revision surgery was necessary 8% of the patients got back to their work prior to the injury.


Assuntos
Artrodese , Articulação Talocalcânea/lesões , Articulação Talocalcânea/cirurgia , Estudos de Coortes , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reoperação , Estudos Retrospectivos , Fatores de Risco , Inquéritos e Questionários , Falha de Tratamento , Indenização aos Trabalhadores
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