RESUMEN

Compartmentalization is crucial for the evolution of life. Present-day phospholipid membranes exhibit a high level of complexity and species-dependent homochirality, the so-called lipid divide. It is possible that less stable, yet more dynamic systems, promoting out-of-equilibrium environments, facilitated the evolution of life at its early stages. The composition of the preceding primitive membranes and the evolutionary route towards complexity and homochirality remain unexplained. Organics-rich carbonaceous chondrites are evidence of the ample diversity of interstellar chemistry, which may have enriched the prebiotic milieu on early Earth. This Review evaluates the detections of simple amphiphiles - likely ancestors of membrane phospholipids - in extraterrestrial samples and analogues, along with potential pathways to form primitive compartments on primeval Earth. The chiroptical properties of the chiral backbones of phospholipids provide a guide for future investigations into the origins of phospholipid membrane homochirality. We highlight a plausible common pathway towards homochirality of lipids, amino acids, and sugars starting from enantioenriched monomers. Finally, given their high recalcitrance and resistance to degradation, lipids are among the best candidate biomarkers in exobiology.

Asunto(s)

Fosfolípidos , Fosfolípidos/química , Evolución Química , Medio Ambiente Extraterrestre/química , Estereoisomerismo , Planeta Tierra , Origen de la Vida , Exobiología

RESUMEN

For the last century, the source of sulfur in Earth's very first organisms has remained a fundamental, unsolved enigma. While sulfates and their organic derivatives with sulfur in the S(+VI) oxidation state represent core nutrients in contemporary biochemistry, the limited bioavailability of sulfates during Earth's early Archean period proposed that more soluble S(+IV) compounds served as the initial source of sulfur for the first terrestrial microorganisms. Here, we reveal via laboratory simulation experiments that the three simplest alkylsulfonic acids-water soluble organic S(+IV) compounds-can be efficiently produced in interstellar, sulfur-doped ices through interaction with galactic cosmic rays. This discovery opens a previously elusive path into the synthesis of vital astrobiological significance and untangles fundamental mechanisms of a facile preparation of sulfur-containing, biorelevant organics in extraterrestrial ices; these molecules can be eventually incorporated into comets and asteroids before their delivery and detection on Earth such as in the Murchison, Tagish Lake, and Allende meteorites along with the carbonaceous asteroid Ryugu.

RESUMEN

Carbohydrates, in particular the d-enantiomers of ribose, 2-deoxyribose, and glucose, are essential to life's informational biopolymers (RNA/DNA) and for supplying energy to living cells through glycolysis. Considered to be potential biosignatures in the search of past or present life, our capacity to detect and quantify these essential sugars is crucial for future space missions to the Moon, Mars or Titan as well as for sample-return missions. However, the enantioselective analysis of carbohydrates is challenging and both research and routine applications, are lacking efficient methods that combine highly sensitive and reproducible detection with baseline enantioselective resolution and reliable enantiomeric excess (ee) measurements. Here, we present four different derivatization strategies in combination with multidimensional gas chromatography coupled to a reflectron time-of-flight mass spectrometer (GC×GC-TOF-MS) for the enantioselective resolution of C3 to C6 carbohydrates potentially suitable for sample-return analyses. Full mass spectral interpretation and calibration curves for one single-step (cyclic boronate derivatives) and three two-step derivatization protocols (aldononitrile-acetate, hemiacetalization-trifluoroacetylation, and hemiacetalization-permethylation) are presented for concentrations ranging from 1 to 50 pmol µL⁻1 with correlation coefficients R2 > 0.94. We compared several analytical parameters including reproducibility, sensitivity (LOD and LOQ), overall separation, chiral resolution (RS), mass spectrum selectivity, stability during long term storage, and reliability of ee measurements to guide the application-dependent selection of optimal separation and quantification performance.

Asunto(s)

Glucosa , Ribosa , Reproducibilidad de los Resultados , Estereoisomerismo , Cromatografía de Gases

RESUMEN

Glycerophospholipid membranes are one of the key cellular components. Still, their species-dependent composition and homochirality remain an elusive subject. In the context of the astrophysical circularly polarized light scenario likely involved in the generation of a chiral bias in meteoritic amino and sugar acids in space, and consequently in the origin of life's homochirality on Earth, this study reports the first measurements of circular dichroism and anisotropy spectra of a selection of glycerophospholipids, their chiral backbones and their analogs. The rather low asymmetry in the interaction of UV/VUV circularly polarized light with sn-glycerol-1/3-phosphate indicates that chiral photons would have been unlikely to directly induce symmetry breaking to membrane lipids. In contrast, the anisotropy spectra of d-3-phosphoglyceric acid and d-glyceraldehyde-3-phosphate unveil up to 20 and 100 times higher maximum anisotropy factor values, respectively. This first experimental report, targeted on investigating the origins of phospholipid symmetry breaking, opens up new avenues of research to explore alternative mechanisms leading to membrane lipid homochirality, while providing important clues for the search for chiral biosignatures of extant and/or extinct life in space, in particular for the ExoMars 2028 mission.

Asunto(s)

Aminoácidos , Glicerofosfolípidos , Estereoisomerismo , Rayos Ultravioleta , Fosfatos

RESUMEN

The photoionization of chiral molecules by elliptically polarized femtosecond laser pulses produces photoelectron angular distributions which show a strong and enantio-sensitive forward/backward asymmetry along the light propagation direction. We report on high precision measurements of this photoelectron elliptical dichroism (PEELD). Using an optical cavity to recycle the laser pulses and increase the signal-to-noise ratio, we determine enantiomeric excesses with a 0.04% precision with a low-power femtosecond laser (4 W) in a compact scheme. We perform momentum-resolved PEELD measurements in 16 molecules, from volatile terpenes to non-volatile amino acids and large iodoarenes. The results demonstrate the high structural sensitivity of PEELD, confirming the spectroscopic interest of this technique. Last, we show how a convolutional neural network can be used to retrieve the chemical and enantiomeric composition of a sample from the momentum-resolved PEELD maps.

RESUMEN

Systematic enrichments of L-amino acids in meteorites is a strong indication that biological homochirality originated beyond Earth. Although still unresolved, stellar UV circularly polarized light (CPL) is the leading hypothesis to have caused the symmetry breaking in space. This involves the differential absorption of left- and right-CPL, a phenomenon called circular dichroism, which enables chiral discrimination. Here we unveil coherent chiroptical spectra of thin films of isovaline enantiomers, the first step towards asymmetric photolysis experiments using a tunable laser set-up. As analogues to amino acids adsorbed on interstellar dust grains, CPL-helicity dependent enantiomeric excesses of up to 2% were generated in isotropic racemic films of isovaline. The low efficiency of chirality transfer from broadband CPL to isovaline could explain why its enantiomeric excess is not detected in the most pristine chondrites. Notwithstanding, small, yet consistent L-biases induced by stellar CPL would have been crucial for its amplification during aqueous alteration of meteorite parent bodies.

Asunto(s)

Meteoroides , Fotoquímica , Aminoácidos/química , Valina

RESUMEN

Propylene oxide, the first chiral molecule recently detected in the interstellar medium, has once again raised the question whether biomolecular chirality might have cosmic origins. However, accurate chiroptical properties of propylene oxide in the ultraviolet spectral range necessary to suggest possible asymmetric synthetic routes in the gas phase are scarce. Here, we report on the first experimental measurements of the anisotropy spectra of gas-phase propylene oxide in the vacuum ultraviolet spectral range. Our experimental results provide novel insights into the handedness of interstellar circular polarization at the dawn of molecular evolution of our star- and planet-forming region. Besides the fundamental importance of this new investigation for understanding the origin and evolution of homochirality on Earth, our high-resolution experimental electronic circular dichroism data will inspire new efforts in quantum computational spectroscopy.

RESUMEN

This work proposes a comprehensive two-dimensional gas chromatography method for the resolution and quantification of 27 amino acids, including 17 enantiomeric pairs, as stable N-trifluoroacetyl-O-methyl ester derivatives. The derivatization approach in combination with enantioselective two-dimensional gas chromatography has proven to be highly responsive with a method detection limit of 1-7 pg even for sterically hindered amino acids such as α,α-dialkylated, and N-alkylated amino acids. Accurate determination of the enantiomeric excess was achieved with errors in the range of ±0.5%-2.5% (1σ) at concentrations ≥10-6 M. A thorough study of the mass spectra of the amino acid derivatives allowed the fragmentation pathways to be distinguished, enabling chromatographic peaks to be unambiguously assigned. The proposed method is particularly suited for applications that require the precise determination of enantiomeric excesses such as those concerning the role of d-amino acid enantiomers in humans, animals, and the environment, as well as for analyses of extraterrestrial samples aimed at understanding the selection of amino acids in stereochemical l-configuration.

Asunto(s)

Aminoácidos , Ésteres , Humanos , Estereoisomerismo , Aminoácidos/análisis , Espectrometría de Masas , Ésteres/análisis , Cromatografía de Gases/métodos

RESUMEN

Electronic circular dichroism (ECD) and anisotropy spectra carry information on differential absorption of left- and right-circularly polarized light (LCPL and RCPL) by optically active compounds. This makes them powerful tools for the rapid determination of enantiomeric excesses (ee) in asymmetric synthetic and pharmaceutical chemistry, as well as for predicting the ee inducible by ultraviolet (UV) CPL. The ECD response of a chiral molecule is, however, critically dependent on the properties of the surrounding medium. Here, we report on the first ECD/anisotropy spectra of aqueous solutions of the calcium salt dihydrate of glyceric acid. A systematic study of the effect of the salt concentration and pH on the chiroptical response revealed significant changes and the appearance of a new ECD band of opposite sign. Based on the literature, this can be rationalized by the increase in the relative proportion of free glyceric acid/glycerate to Ca2+ complexes with glycerate with decreasing salt concentration or pH. Glyceric acid can be readily produced under astrophysical conditions. The anisotropy spectra of the solution containing prevalently the free form of this dihydroxy carboxylic acid resemble the ones of previously investigated aliphatic chain hydroxycarboxylic acids and proteinogenic amino acids. This indicates possible common handedness of stellar CPL-induced asymmetry in the potential comonomers of primitive proto-peptides.

Asunto(s)

Calcio , Electrónica , Anisotropía , Dicroismo Circular , Ácidos Glicéricos , Concentración de Iones de Hidrógeno , Estereoisomerismo

RESUMEN

Circularly polarised light (CPL) interacting with interstellar organic molecules might have imparted chiral bias and hence preluded prebiotic evolution of biomolecular homochirality. The L-enrichment of extra-terrestrial amino acids in meteorites, as opposed to no detectable excess in monocarboxylic acids and amines, has previously been attributed to their intrinsic interaction with stellar CPL revealed by substantial differences in their chiroptical signals. Recent analyses of meteoritic hydroxycarboxylic acids (HCAs) - potential co-building blocks of ancestral proto-peptides - indicated a chiral bias toward the L-enantiomer of lactic acid. Here we report on novel anisotropy spectra of several HCAs using a synchrotron radiation electronic circular dichroism spectrophotometer to support the re-evaluation of chiral biomarkers of extra-terrestrial origin in the context of absolute photochirogenesis. We found that irradiation by CPL which would yield L-excess in amino acids would also yield L-excess in aliphatic chain HCAs, including lactic acid and mandelic acid, in the examined conditions. Only tartaric acid would show "unnatural" D-enrichment, which makes it a suitable target compound for further assessing the relevance of the CPL scenario.

RESUMEN

Wavelength-dependent measurements of the RNA base uracil, undertaken with nanosecond ultraviolet laser pulses, have previously identified a fragment at m/z = 84 (corresponding to the C3H4N2O+ ion) at excitation wavelengths ≤232 nm. This has been interpreted as a possible signature of a theoretically predicted ultrafast ring-opening occurring on a neutral excited state potential energy surface. To further investigate the dynamics of this mechanism, and also the non-adiabatic dynamics operating more generally in uracil, we have used a newly built ultra-high vacuum spectrometer incorporating a laser-based thermal desorption source to perform time-resolved ion-yield measurements at pump wavelengths of 267 nm, 220 nm, and 200 nm. We also report complementary data obtained for the related species 2-thiouracil following 267 nm excitation. Where direct comparisons can be made (267 nm), our findings are in good agreement with the previously reported measurements conducted on these systems using cold molecular beams, demonstrating that the role of initial internal energy on the excited state dynamics is negligible. Our 220 nm and 200 nm data also represent the first reported ultrafast study of uracil at pump wavelengths <250 nm, revealing extremely rapid (<200 fs) relaxation of the bright S3(1ππ*) state. These measurements do not, however, provide any evidence for the appearance of the m/z = 84 fragment within the first few hundred picoseconds following excitation. This key finding indicates that the detection of this specific species in previous nanosecond work is not directly related to an ultrafast ring-opening process. An alternative excited state process, operating on a more extended time scale, remains an open possibility.

RESUMEN

We developed a method for sensitive elemental analysis of wines using laser-induced breakdown spectroscopy (LIBS). In order to overcome the inefficiency of direct ablation of bulk wine (an organic liquid), a thin layer of wine residue was prepared on a metallic target according to an appropriated heating procedure applied to an amount of liquid wine dropped on the target surface. The obtained ensemble was thus ablated. Such a sample preparation procedure used a very small volume of 2 mL of wine and took only 30 min without reagent or solvent. The results show the detection of tens of metal and non-metal elements including majors (Na, Mg, K, Ca), minors, and traces (Li, B, Si, P, Ti, Mn, Fe, Cu, Zn, Rb, Sr, Ba, and Pb) in wines purchased from local supermarkets and from different production places in France. Commercially available wines were then spiked with certified standard solutions of Ti and Fe. Three series of laboratory reference samples were thus prepared using three different wines (a red wine and a white wine from a same production region and a red wine from another production region) with concentrations of Ti and Fe in the range of 1-40 mg/L. Calibration graphs established with the spiked samples allowed extracting the figures-of-merit parameters of the method for wine analysis such as the coefficient of determination ( R2) and the limits of detection and quantification (LOD and LOQ). The calibration curves built with the three wines were then compared. We studied the residual matrix effect between these wines in the determination of the concentrations of Ti and Fe.

RESUMEN

AIMS AND OBJECTIVES: To establish the availability of High Efficiency Particulate Air (HEPA)- and nonHEPA-filtered rooms in eastern European transplant centres and to investigate the impact on incidence of pneumonia and mortality after haematopoietic stem cell transplantation (HSCT). BACKGROUND: Barrier nursing in HEPA-filtered rooms is generally recommended for patients undergoing HSCT. There are only limited data on the availability of HEPA-filtered rooms and the impact on incidence of pneumonia and mortality. DESIGN: A prospective, observational, international study. METHODS: Monitoring cards were distributed within the East Forum EBMT-Nurses Group cooperating centres, and 689 consecutive patients were registered in 1/2010-6/2012. Patients were monitored for 100 days post-transplant. RESULTS: In patients undergoing autologous HSCT, pneumonia developed in 14/400 (3·5%) and was the cause of death in 2/14 (14%) of patients. There was no significant difference in mortality between HEPA-filtered and nonHEPA-filtered groups (4·5% vs. 4·9%, respectively). 239/400 (59%) transplantations were performed in single-bed rooms [190/239 (79%) HEPA-filtered] and 161 (41%) in two-bed rooms [28/161 (17%) HEPA-filtered]. In allogeneic transplantation, pneumonia developed in 24/289 (8·3%) and was the cause of death in 11/24 (45%) of patients. There was no significant difference in mortality between HEPA-filtered and non-HEPA-filtered groups (14% vs. 17%, respectively). 281/289 (97%) of allogeneic transplantations were performed in single-bed rooms [254/281 (90%) HEPA-filtered], and pneumonia was more frequent in patients on corticosteroids and in rooms without HEPA. CONCLUSION: The incidence of pneumonia in the autologous transplantation setting is low. More pneumonia was observed in the allogeneic HSCT group, especially in patients on corticosteroids. There was a trend towards a lower incidence of pneumonia in allogeneic HSCT patients treated in HEPA-filtered rooms. RELEVANCE TO CLINICAL PRACTICE: Autologous HSCT transplantation may safely be performed without HEPA filtration. HEPA filtration might be preferable in patients undergoing allogeneic transplantation.

Asunto(s)

Trasplante de Células Madre Hematopoyéticas , Aislamiento de Pacientes , Habitaciones de Pacientes , Neumonía/epidemiología , Adolescente , Adulto , Anciano , Europa (Continente)/epidemiología , Femenino , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Neumonía/etiología , Neumonía/enfermería , Neumonía/prevención & control , Estudios Prospectivos , Adulto Joven

RESUMEN

PURPOSE: Oral mucositis (OM) still represents a significant complication of hematopoietic stem cell transplantations (HSCT). Observational studies focusing on risk factor definitions are still warranted. METHOD: A total of 126 patients participated in this observational study after autologous HSCT with the BEAM and HD-l-PAM 200mg/m(2) conditioning regimens. Basic clinical and laboratory variables and their impact on OM were assessed. RESULTS: Age, gender, body mass index, and baseline absolute neutrophil counts were not shown to have any negative impact on OM development. The multivariate analysis revealed oral cryotherapy non-provision as being the most significant predictor for OM incidence (p < 0.0001), followed by BEAM conditioning regimen (p = 0.007), OM in a patient's history (p = 0.002) and lower number of days since the last chemotherapy (p = 0.025). The cryotherapy was remarkably effective both in the single high-dose melphalan 200mg/m(2) conditioning regimen (18% OM in cryotherapy vs. 68% without it, p<0.0001) and in the multidrug BEAM (melphalan 140mg/m(2)) regimen (38% vs. 86%, p=0.006). CONCLUSION: Oral cryotherapy should be implemented into supportive care management in patients treated with high-dose melphalan short-infusion chemotherapy. Large and well-designed randomized trials are necessary to obtain more significant and reliable results and understanding regarding OM risk factors.

Asunto(s)

Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Crioterapia , Trasplante de Células Madre Hematopoyéticas , Estomatitis/prevención & control , Adolescente , Adulto , Anciano , Protocolos de Quimioterapia Combinada Antineoplásica/administración & dosificación , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Carmustina/administración & dosificación , Carmustina/efectos adversos , Citarabina/administración & dosificación , Citarabina/efectos adversos , Relación Dosis-Respuesta a Droga , Esquema de Medicación , Etopósido/administración & dosificación , Etopósido/efectos adversos , Femenino , Trasplante de Células Madre Hematopoyéticas/efectos adversos , Humanos , Masculino , Melfalán/administración & dosificación , Melfalán/efectos adversos , Persona de Mediana Edad , Estudios Prospectivos , Factores de Riesgo , Estomatitis/etiología , Acondicionamiento Pretrasplante/efectos adversos , Acondicionamiento Pretrasplante/métodos , Trasplante Autólogo , Resultado del Tratamiento , Adulto Joven

RESUMEN

Antimicrobial solutions are widely used in the nursing care of chemotherapy induced oral mucositis (OM). There is little evidence, however, supporting their use for reducing mucosal damage. In our study, 132 patients were randomized to use normal saline (n=65) or povidone-iodine diluted 1:100 (n=67) mouthwashes for OM prophylaxis and treatment after high-dose chemotherapy comprising BEAM or HD-L-PAM followed by autologous peripheral stem cell transplantation. The study groups were well balanced in respect of age, sex, chemotherapy and the number of CD34+ cells in the graft. No significant difference was found between the groups in respect of OM characteristics, fever of unknown origin (FUO) and other infections. The antimicrobial solution was less tolerable for patients. OM occurred significantly more often in females than in males (86% vs 60%, P=0.0016) and was worse and of longer duration. The mechanical effect of mouthwashes might have a certain importance in FUO prevention. When indicating oral rinses, the patient's individual preference and tolerance of solutions offered should be considered.

Asunto(s)

Antiinfecciosos Locales/uso terapéutico , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Mucosa Bucal/patología , Povidona Yodada/uso terapéutico , Cloruro de Sodio/uso terapéutico , Estomatitis/tratamiento farmacológico , Adulto , Anciano , Antiinfecciosos Locales/administración & dosificación , Protocolos de Quimioterapia Combinada Antineoplásica/administración & dosificación , Carmustina/administración & dosificación , Citarabina/administración & dosificación , Etopósido/administración & dosificación , Femenino , Humanos , Masculino , Melfalán/administración & dosificación , Persona de Mediana Edad , Antisépticos Bucales , Trasplante de Células Madre de Sangre Periférica , Povidona Yodada/administración & dosificación , Factores Sexuales , Cloruro de Sodio/administración & dosificación , Trasplante Autólogo

RESUMEN

OBJECTIVE: The hospitalization rate for bronchiolitis of any cause among US children younger than 1 year is estimated at 31.2 per 1000. No data exist on respiratory syncytial virus (RSV)-specific hospitalization rates among high-risk Native Americans other than Alaska Natives, for whom the incidence of RSV hospitalization was estimated at 150 per 1000 among infants younger than 1 year. We aimed to estimate RSV hospitalization rates among Navajo and White Mountain Apache children younger than 2 years. METHODS: We conducted prospective population-level hospital-based surveillance to determine RSV hospitalization rates among Navajo and White Mountain Apache children younger than 2 years. From 1997 to 2000, all children who were admitted for acute lower respiratory tract infection between October 1 and March 31 had a nasopharyngeal aspirate obtained and tested for RSV by commercial enzyme immunoassay kits. We reviewed charts of children who tested positive for RSV antigen to determine disease severity. RESULTS: During 3 RSV seasons (1997-2000), 51.3% of 1837 admissions for acute lower respiratory tract infection among children younger than 2 years were attributed to RSV infection. The overall seasonal RSV hospitalization rate among children younger than 2 years was 63.6 per 1000 and 91.3 per 1000 among children younger than 1 year. In a univariate analysis, predictors of severity included age <6 months (relative risk: 6.8; 95% confidence interval: 3.1-17.0). CONCLUSIONS: Navajo and White Mountain Apache children are at high risk for RSV disease requiring hospitalization. A lower threshold for hospitalization or underlying chronic conditions that predispose to severe RSV disease do not seem to explain high RSV hospitalization rates in this population.

Asunto(s)

Indígenas Norteamericanos/estadística & datos numéricos , Infecciones por Virus Sincitial Respiratorio/epidemiología , Hospitalización/estadística & datos numéricos , Humanos , Lactante , Modelos Logísticos , Vigilancia de la Población , Estudios Prospectivos , Infecciones por Virus Sincitial Respiratorio/etnología , Factores de Riesgo , Índice de Severidad de la Enfermedad , Estados Unidos/epidemiología