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1.
BMC Genomics ; 24(1): 19, 2023 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-36639634

RESUMO

BACKGROUND: Adaptations by arthropod pests to host plant defenses of crops determine their impacts on agricultural production. The larval host range of western corn rootworm, Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), is restricted to maize and a few grasses. Resistance of D. v. virgifera to crop rotation practices and multiple insecticides contributes to its status as the most damaging pest of cultivated maize in North America and Europe. The extent to which adaptations by this pest contributes to host plant specialization remains unknown. RESULTS: A 2.42 Gb draft D. v. virgifera genome, Dvir_v2.0, was assembled from short shotgun reads and scaffolded using long-insert mate-pair, transcriptome and linked read data. K-mer analysis predicted a repeat content of ≥ 61.5%. Ortholog assignments for Dvir_2.0 RefSeq models predict a greater number of species-specific gene duplications, including expansions in ATP binding cassette transporter and chemosensory gene families, than in other Coleoptera. A majority of annotated D. v. virgifera cytochrome P450s belong to CYP4, 6, and 9 clades. A total of 5,404 transcripts were differentially-expressed between D. v. virgifera larvae fed maize roots compared to alternative host (Miscanthus), a marginal host (Panicum virgatum), a poor host (Sorghum bicolor) and starvation treatments; Among differentially-expressed transcripts, 1,908 were shared across treatments and the least number were between Miscanthus compared to maize. Differentially-expressed transcripts were enriched for putative spliceosome, proteosome, and intracellular transport functions. General stress pathway functions were unique and enriched among up-regulated transcripts in marginal host, poor host, and starvation responses compared to responses on primary (maize) and alternate hosts. CONCLUSIONS: Manual annotation of D. v. virgifera Dvir_2.0 RefSeq models predicted expansion of paralogs with gene families putatively involved in insecticide resistance and chemosensory perception. Our study also suggests that adaptations of D. v. virgifera larvae to feeding on an alternate host plant invoke fewer transcriptional changes compared to marginal or poor hosts. The shared up-regulation of stress response pathways between marginal host and poor host, and starvation treatments may reflect nutrient deprivation. This study provides insight into transcriptomic responses of larval feeding on different host plants and resources for genomic research on this economically significant pest of maize.


Assuntos
Besouros , Inseticidas , Animais , Zea mays/fisiologia , Besouros/genética , Larva/metabolismo , Poaceae/genética , Inseticidas/metabolismo , Controle Biológico de Vetores , Plantas Geneticamente Modificadas/genética , Endotoxinas
2.
J Am Chem Soc ; 145(25): 14070-14086, 2023 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-37327324

RESUMO

Femtosecond time-resolved X-ray absorption (XANES) at the Co K-edge, X-ray emission (XES) in the Co Kß and valence-to-core regions, and broadband UV-vis transient absorption are combined to probe the femtosecond to picosecond sequential atomic and electronic dynamics following photoexcitation of two vitamin B12 compounds, hydroxocobalamin and aquocobalamin. Polarized XANES difference spectra allow identification of sequential structural evolution involving first the equatorial and then the axial ligands, with the latter showing rapid coherent bond elongation to the outer turning point of the excited state potential followed by recoil to a relaxed excited state structure. Time-resolved XES, especially in the valence-to-core region, along with polarized optical transient absorption suggests that the recoil results in the formation of a metal-centered excited state with a lifetime of 2-5 ps. This combination of methods provides a uniquely powerful tool to probe the electronic and structural dynamics of photoactive transition-metal complexes and will be applicable to a wide variety of systems.

3.
J Vasc Interv Radiol ; 34(12): 2155-2161, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37619941

RESUMO

PURPOSE: To develop a machine-learned algorithm to predict the risk of postlung biopsy pneumothorax requiring chest tube placement (CTP) to facilitate preprocedural decision making, optimize patient care, and improve resource allocation. MATERIALS AND METHODS: This retrospective study collected clinical and imaging features of biopsy samples obtained from patients with lung nodule biopsy and included information from 59 procedures resulting in pneumothorax requiring CTP and randomly selected 67 procedures without CTP (convenience sample). The data were divided into 70 and 30 as training and testing sets, respectively. Conventional machine-learned binary classifiers were explored with preprocedural imaging and clinical data as input features and CTP as the output. RESULTS: There was no single pathognomonic imaging or predictive clinical feature. For the independent test set under the high-specificity mode, a decision tree, logistic regression, and Naïve Bayes classifier achieved accuracies of identifying CTP at 0.79, 0.93, and 0.89 and area under receiver operating curves (AUROCs) of 0.68, 0.76, and 0.82, respectively. Under high-sensitivity mode, a decision tree, logistic regression, and Naïve Bayes achieved accuracies of identifying CTP of 0.60, 0.45, and 0.60 with AUROCs of 0.71, 0.81, and 0.82, respectively. High importance features included lesion character, chronic obstructive pulmonary disease, lesion depth, and age. A coarse decision tree requiring 4 inputs achieved comparable performance as other methods and previous machine learning prediction studies. CONCLUSIONS: The results support the possibility of predicting pneumothorax requiring CTP after biopsy based on an automated decision support, reliant on readily available preprocedural information.


Assuntos
Pneumotórax , Humanos , Pneumotórax/diagnóstico por imagem , Pneumotórax/etiologia , Pneumotórax/terapia , Estudos Retrospectivos , Tubos Torácicos , Teorema de Bayes , Biópsia por Agulha/métodos , Biópsia/efeitos adversos , Pulmão/diagnóstico por imagem , Pulmão/patologia , Algoritmos
4.
J Prosthet Dent ; 129(4): 523-526, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34344527

RESUMO

This article describes a restorative solution for implants placed at an insufficient depth and in a patient with limited interarch space, making the esthetics, emergence profile, and retention of a cemented restoration problematic. These challenges were overcome by adhesively bonding a pressed lithium disilicate veneer to a custom cast metal abutment veneered with a thin layer of feldspathic porcelain. The ceramic veneer with the attached core engaged a facially located screw-access channel, which increased retention and resistance form and facilitated seating of the veneer. Adhesive bonding via the application of a thin layer of feldspathic porcelain on the custom dental implant abutment was also used to overcome the lack of resistance form with a veneer preparation.


Assuntos
Implantes Dentários , Porcelana Dentária , Humanos , Estética Dentária , Cerâmica , Coroas
5.
Pediatr Res ; 92(6): 1566-1574, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-35288639

RESUMO

BACKGROUND: The increasing magnitude of the opioid crisis and rising rates of neonatal abstinence syndrome (NAS) diagnoses highlight the need for increased research into how maternal substance use during pregnancy can impact the neonatal immune profile and its functionality. We hypothesized that neonates with opioid exposure would have reduced proportions of some immune cells, an anti-inflammatory cytokine profile, reduced T cell proliferation, and monocyte bacterial killing activity compared to the control population. METHODS: The present study compares immune cell populations, inflammatory and anti-inflammatory cytokine and chemokine levels in the serum, and monocyte and T cell functional activity using umbilical cord samples from neonates with known opioid exposure during gestation and from control neonates without known exposure. RESULTS: Our findings demonstrated a significant reduction in neutrophils, decreased levels of inflammatory cytokines in the serum, and reduced IL-2 production during in vitro CD4+ T cell proliferation in neonates exposed to opioids compared to controls. The neutrophil findings were supported by retrospective analysis of an extended network of deidentified patient records. CONCLUSIONS: This study is the first of its kind to evaluate differences in neonatal immunity as a result of opioid exposure in the human population that will inform continued mechanistic studies. IMPACT: The opioid epidemic has become a public health crisis in the United States, and the corresponding incidence of neonatal abstinence syndrome (NAS) have risen accordingly. New research is required to understand the short and long-term health impacts of opioid exposure to the neonate. This is the first human study to investigate the immunologic profile and functionality in neonates with known opioid exposure in utero. The abundance of neutrophils and the ratio of neutrophils to lymphocytes is significantly reduced along with inflammatory cytokines and chemokines following opioid exposure during pregnancy. The immune profile in opioid-exposed neonates may promote susceptibility to infection.


Assuntos
Síndrome de Abstinência Neonatal , Transtornos Relacionados ao Uso de Opioides , Complicações na Gravidez , Gravidez , Recém-Nascido , Feminino , Humanos , Estados Unidos , Analgésicos Opioides/efeitos adversos , Síndrome de Abstinência Neonatal/tratamento farmacológico , Estudos Retrospectivos , Transtornos Relacionados ao Uso de Opioides/diagnóstico , Complicações na Gravidez/diagnóstico
6.
BMC Genomics ; 22(1): 639, 2021 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-34479486

RESUMO

BACKGROUND: Resistance of pest insect species to insecticides, including B. thuringiensis (Bt) pesticidal proteins expressed by transgenic plants, is a threat to global food security. Despite the western corn rootworm, Diabrotica virgifera virgifera, being a major pest of maize and having populations showing increasing levels of resistance to hybrids expressing Bt pesticidal proteins, the cell mechanisms leading to mortality are not fully understood. RESULTS: Twenty unique RNA-seq libraries from the Bt susceptible D. v. virgifera inbred line Ped12, representing all growth stages and a range of different adult and larval exposures, were assembled into a reference transcriptome. Ten-day exposures of Ped12 larvae to transgenic Bt Cry3Bb1 and Gpp34/Tpp35Ab1 maize roots showed significant differential expression of 1055 and 1374 transcripts, respectively, compared to cohorts on non-Bt maize. Among these, 696 were differentially expressed in both Cry3Bb1 and Gpp34/Tpp35Ab1 maize exposures. Differentially-expressed transcripts encoded protein domains putatively involved in detoxification, metabolism, binding, and transport, were, in part, shared among transcripts that changed significantly following exposures to the entomopathogens Heterorhabditis bacteriophora and Metarhizium anisopliae. Differentially expressed transcripts in common between Bt and entomopathogen treatments encode proteins in general stress response pathways, including putative Bt binding receptors from the ATP binding cassette transporter superfamily. Putative caspases, pro- and anti-apoptotic factors, as well as endoplasmic reticulum (ER) stress-response factors were identified among transcripts uniquely up-regulated following exposure to either Bt protein. CONCLUSIONS: Our study suggests that the up-regulation of genes involved in ER stress management and apoptotic progression may be important in determining cell fate following exposure of susceptible D. v. virgifera larvae to Bt maize roots. This study provides novel insights into insect response to Bt intoxication, and a possible framework for future investigations of resistance mechanisms.


Assuntos
Bacillus thuringiensis , Besouros , Praguicidas , Animais , Bacillus thuringiensis/genética , Sobrevivência Celular , Besouros/genética , Endotoxinas/toxicidade , Resistência a Inseticidas , Larva/genética , Controle Biológico de Vetores , Plantas Geneticamente Modificadas/genética , Regulação para Cima , Zea mays/genética
7.
Am J Med Genet C Semin Med Genet ; 187(1): 37-47, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33270363

RESUMO

The advent of next generation DNA sequencing (NGS) has revolutionized clinical medicine by enabling wide-spread testing for genomic anomalies and polymorphisms. With that explosion in testing, however, come several informatics challenges including managing large amounts of data, interpreting the results and providing clinical decision support. We present Flype, a web-based bioinformatics platform built by a small group of bioinformaticians working in a community hospital setting, to address these challenges by allowing us to: (a) securely accept data from a variety of sources, (b) send orders to a variety of destinations, (c) perform secondary analysis and annotation of NGS data, (d) provide a central repository for all genomic variants, (e) assist with tertiary analysis and clinical interpretation, (f) send signed out data to our EHR as both PDF and discrete data elements, (g) allow population frequency analysis and (h) update variant annotation when literature knowledge evolves. We discuss the multiple use cases Flype supports such as (a) in-house NGS tests, (b) in-house pharmacogenomics (PGX) tests, (c) dramatic scale-up of genomic testing using an external lab, (d) consumer genomics using two external partners, and (e) a variety of reporting tools. The source code for Flype is available upon request to the authors.


Assuntos
Medicina de Precisão , Software , Genômica , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Farmacogenética
8.
J Hepatol ; 74(6): 1286-1294, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33326815

RESUMO

BACKGROUND & AIMS: Alcohol use treatment such as medication-assisted therapies (MATs) and counseling are available and effective in promoting alcohol abstinence. We sought to explore the cost-effectiveness of different alcohol use treatments among patients with compensated alcohol-related cirrhosis (AC). METHODS: We simulated a cohort of patients with compensated AC receiving care from a hepatology clinic over their lifetimes. We estimated costs (in 2017 US$) and benefits in terms of quality-adjusted life years (QALYs) gained from healthcare and societal perspectives. Transition probabilities, costs, and health utility weights were taken from the literature. Treatment effects of FDA-approved MATs (acamprosate and naltrexone) and non-FDA approved MATs (baclofen, gabapentin, and topiramate) and counseling were based on a study of employer-insured patients with AC. We calculated incremental cost-effectiveness ratios (ICERs) and performed one-way and probabilistic sensitivity analyses to understand the impact of parameter uncertainty. RESULTS: Compared to a do-nothing scenario, MATs and counseling were found to be cost-saving from a healthcare perspective, which means that they provide more benefits with less costs than no intervention. Compared to other interventions, acamprosate and naltrexone cost the least and provide the most QALYs. If the effectiveness of MATs and counseling decreased, these interventions would still be cost-effective based on the commonly used $100,000 per QALY gained threshold. Several sensitivity and scenario analyses showed that our main findings are robust. CONCLUSIONS: Among patients with compensated AC, MATs and counseling are extremely cost-effective, and in some cases cost-saving, interventions to prevent decompensation and improve health. Health policies (e.g. payer reimbursement) should emphasize and appropriately compensate for these interventions. LAY SUMMARY: Alcohol use treatments, including physician counseling and medication-assisted therapies (MATs), improve the outcomes of patients with compensated alcohol-related cirrhosis, though use and access have remained suboptimal. In this study, we found that counseling and MATs are extremely cost-effective, and in some cases cost-saving, interventions to help patients with alcohol-related cirrhosis abstain from alcohol and improve their health. Wider use of these interventions should be encouraged.


Assuntos
Acamprosato/economia , Acamprosato/uso terapêutico , Dissuasores de Álcool/economia , Dissuasores de Álcool/uso terapêutico , Alcoolismo/complicações , Alcoolismo/tratamento farmacológico , Análise Custo-Benefício/métodos , Cirrose Hepática Alcoólica/complicações , Naltrexona/economia , Naltrexona/uso terapêutico , Idoso , Estudos de Coortes , Feminino , Custos de Cuidados de Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Anos de Vida Ajustados por Qualidade de Vida , Resultado do Tratamento
9.
Ann Plast Surg ; 86(4): 421-423, 2021 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-32881751

RESUMO

ABSTRACT: The authors present 3 unique cases of complex fistula formations because of orbital fracture repair with a Teflon (polytetrafluroethylene) implant. A 26-year-old man presented with dacryocystitis and a cutaneous fistula 8 years after left orbital floor and medial wall fracture repair with a Teflon implant. A 46-year-old woman suffered orbital trauma after a motor vehicle accident as a teenager and the fracture was repaired with Teflon implant. Thirty-two years later, she presented with lower eyelid fistula, ectropion, and retraction. A 65-year-old woman also previously had Teflon implants for the repair of her left inferior and lateral orbital rim after a motor vehicle accident. Twenty-five years later, she presented with chronic infections involving the repaired areas, as well as left lower lid ectropion and fistula formation. The woven material nature of Teflon acted as a nidus for infection, inflammation, and led to complex cutaneous fistula formations in these patients.


Assuntos
Doenças Orbitárias , Fraturas Orbitárias , Adolescente , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Órbita , Fraturas Orbitárias/etiologia , Fraturas Orbitárias/cirurgia , Politetrafluoretileno/efeitos adversos , Próteses e Implantes
11.
Inorg Chem ; 59(9): 6422-6431, 2020 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-32311266

RESUMO

Alkynylcorrinoids are a class of organometallic B12 derivatives, recently rediscovered for use as antivitamins B12 and as core components of B12-based biological vectors. They feature exceptional photochemical and thermal stability of their characteristic extra-short Co-C bond. We describe here the synthesis and structure of 3-hydroxypropynylcobalamin (HOPryCbl) and photochemical experiments with HOPryCbl, as well as of the related alkynylcobalamins: phenylethynylcobalamin and difluoro-phenylethynylcobalamin. Ultrafast spectroscopic studies of the excited state dynamics and mechanism for ground state recovery demonstrate that the Co-C bond of alkynylcobalamins is stable, with the Co-N bond and ring deformations mediating internal conversion and ground state recovery within 100 ps. These studies provide insights required for the rational design of photostable or photolabile B12-based cellular vectors.


Assuntos
Carbono/química , Cobalto/química , Vitamina B 12/química , Cristalografia por Raios X , Teoria da Densidade Funcional , Modelos Moleculares , Conformação Molecular , Processos Fotoquímicos , Temperatura , Vitamina B 12/análogos & derivados , Vitamina B 12/síntese química
12.
Pestic Biochem Physiol ; 164: 165-172, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32284123

RESUMO

Western corn rootworm (WCR) pyrethroid resistance has been previously reported in the United States (US) western Corn Belt, and cross-resistance and synergism studies suggested that both target site insensitivity and enhanced metabolism may be conferring WCR resistance to pyrethroids. The present study aimed to investigate the potential mechanisms of WCR pyrethroid resistance and to estimate the heritability of the resistance trait. Biochemical assays using model substrates and spectrophotometry revealed 2-4-fold higher activity of P450s and esterases in pyrethroid-resistant WCR populations, whereas the biological activity of glutathione S-transferase was similar between populations tested. No mutation in the voltage-gated sodium channel was detected in pyrethroid-resistant WCR individuals by sequencing PCR products containing the para-homologous L1014, T929, and M918 amino acid positions that are commonly associated with target site mutations in other pyrethroid-resistant insects. A pilot estimation of pyrethroid resistance heritability obtained during laboratory selection of a WCR population suggested a major genetic component of the resistance trait and predicted a 10-fold increase in WCR bifenthrin resistance within ~7 generations of insecticide lethal exposure. Results support earlier indirect evidence that enhanced metabolism may be contributing to WCR resistance to pyrethroids and illustrates the potential of WCR pyrethroid resistance evolution.


Assuntos
Besouros , Inseticidas , Piretrinas , Animais , Resistência a Inseticidas , Larva , Zea mays
13.
J Pediatr ; 212: 102-110.e5, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31230888

RESUMO

OBJECTIVE: To determine the risk of bacterial meningitis in infants aged 29-90 days with evidence of urinary tract infection (UTI). METHODS: PubMed (MEDLINE), Embase, and the Cochrane Library were systematically searched for studies reporting rates of meningitis in infants aged 29-90 days with abnormal urinalysis or urine culture. Observational studies in infants with evidence of UTI who underwent lumbar puncture (LP) reporting age-specific event rates of bacterial meningitis and sterile cerebrospinal fluid pleocytosis were included. Prevalence estimates for bacterial meningitis in infants with UTI were pooled in a random effects meta-analysis. RESULTS: Three prospective and 17 retrospective cohort studies were included in the meta-analysis. The pooled prevalence of concomitant bacterial meningitis in infants with UTI was 0.25% (95% CI, 0.09%-0.70%). Rates of sterile pleocytosis ranged from 0% to 29%. Variation in study methods precluded calculation of a pooled estimate for sterile pleocytosis. In most studies, the decision to perform a LP was up to the provider, introducing selection bias into the prevalence estimate. CONCLUSIONS: The risk of bacterial meningitis in infants aged 29-90 days with evidence of UTI is low. A selective approach to LP in infants identified as low risk for meningitis by other clinical criteria may be indicated.


Assuntos
Meningites Bacterianas/epidemiologia , Infecções Urinárias/epidemiologia , Antibacterianos/administração & dosagem , Humanos , Lactente , Recém-Nascido , Meningites Bacterianas/líquido cefalorraquidiano , Meningites Bacterianas/etiologia , Medição de Risco , Punção Espinal/efeitos adversos , Infecções Urinárias/microbiologia
16.
J Phys Chem A ; 122(38): 7548-7558, 2018 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-30230333

RESUMO

All isomers of a four stage rotary molecular motor, dimethyl-tetrahydro-bi(cyclopenta[α]napthal-enylidene), are studied with ultrafast transient absorption spectroscopy. Single and two pulse excitations (pump and delayed repump with a different wavelength) are used to optically probe the excited state dynamics. These measurements demonstrate that this motor is not only designed for unidirectional isomerization, but is also "primed" for efficient rotary motion. The yield for photoisomerization from the stable P-cis isomer to the metastable M-trans isomer is 85% ± 10%, while the yield for the undesired back reaction is ca. 0.08 (+0.02, -0.05). The yield for photoisomerization from stable P-trans to the metastable M-cis isomer is ca. 85% ± 3% and the yield for the back reaction is 15% ± 3%. Excitation of P-trans in the lowest singlet state results in formation of a dark state on a 3.6 ps time scale and formation of the M-cis isomer on a ca. 12 ps time scale. Excitation of P-cis in the lowest singlet state results in formation of a dark state on ca. 13 ps time scale and formation of the M-trans isomer on a 71 ps time scale. Excitation of either isomer at 269 nm, higher in the excited state manifold, accesses additional excited state pathways, but does not change the ultimate product formation. This result suggests that pulse sequences accessing higher excited states may provide a tool to manipulate the molecular motor. Pulse sequences using a 269 nm pump pulse and a 404 nm repump pulse are able to increase the yield of the P-cis to M-trans reaction but only decrease the yield of the P-trans to M-cis reaction. These pulse sequences are unable to access reaction pathways that bypass the helix inversion step, although other wavelengths and time delays might yet provide optical control of the entire reaction cycle. We propose intermediates and candidate conical intersections between all four isomers.

17.
J Phys Chem A ; 122(33): 6693-6703, 2018 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-30106572

RESUMO

Ultrafast time-resolved spectroscopy was used to study the photochemistry of hydroxocobalamin (HOCbl) and aquocobalamin (H2OCbl+) in solution. Spectroscopic measurements and TD-DFT simulations provide a consistent picture of the spectroscopy and photochemistry. Excitation of H2OCbl+ results in formation of an excited state followed by rapid internal conversion to the ground state (0.35 ± 0.15 ps) through an S1/S0 seam at a slightly elongated Co-O bond length and a significantly elongated Co-NIm bond length. In contrast, the initial elongation of the axial bonds in HOCbl is followed by contraction to an excited state minimum with bonds slightly shorter than those in the ground state. Internal conversion to the ground state follows on a picosecond time scale (5.3 ± 0.4 ps). For both compounds, photodissociation forming cob(II)alamin and hydroxyl radicals (∼1.5% yield) requires excitation to highly excited states. Dissociation is mediated by competition between internal conversion to the S1 surface and prompt bond cleavage.

18.
J Phys Chem A ; 122(22): 4963-4971, 2018 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-29799204

RESUMO

Polarized ultrafast time-resolved X-ray absorption near edge structure (XANES) allows characterization of excited state dynamics following excitation. Excitation of vitamin B12, cyanocobalamin (CNCbl), in the αß-band at 550 nm and the γ-band at 365 nm was used to uniquely resolve axial and equatorial contributions to the excited state dynamics. The structural evolution of the excited molecule is best described by a coherent ballistic trajectory on the excited state potential energy surface. Prompt expansion of the Co cavity by ca. 0.03 Å is followed by significant elongation of the axial bonds (>0.25 Å) over the first 190 fs. Subsequent contraction of the Co cavity in both axial and equatorial directions results in the relaxed S1 excited state structure within 500 fs of excitation.

19.
Biophys J ; 112(6): 1282-1289, 2017 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-28355554

RESUMO

The Gram-negative Bdellovibrio bacteriovorus (BV) is a model bacterial predator that hunts other bacteria and may serve as a living antibiotic. Despite over 50 years since its discovery, it is suggested that BV probably collides into its prey at random. It remains unclear to what degree, if any, BV uses chemical cues to target its prey. The targeted search problem by the predator for its prey in three dimensions is a difficult problem: it requires the predator to sensitively detect prey and forecast its mobile prey's future position on the basis of previously detected signal. Here instead we find that rather than chemically detecting prey, hydrodynamics forces BV into regions high in prey density, thereby improving its odds of a chance collision with prey and ultimately reducing BV's search space for prey. We do so by showing that BV's dynamics are strongly influenced by self-generated hydrodynamic flow fields forcing BV onto surfaces and, for large enough defects on surfaces, forcing BV in orbital motion around these defects. Key experimental controls and calculations recapitulate the hydrodynamic origin of these behaviors. While BV's prey (Escherichia coli) are too small to trap BV in hydrodynamic orbit, the prey are also susceptible to their own hydrodynamic fields, substantially confining them to surfaces and defects where mobile predator and prey density is now dramatically enhanced. Colocalization, driven by hydrodynamics, ultimately reduces BV's search space for prey from three to two dimensions (on surfaces) even down to a single dimension (around defects). We conclude that BV's search for individual prey remains random, as suggested in the literature, but confined, however-by generic hydrodynamic forces-to reduced dimensionality.


Assuntos
Bdellovibrio bacteriovorus/fisiologia , Hidrodinâmica , Escherichia coli/fisiologia , Processos Estocásticos
20.
J Am Chem Soc ; 139(5): 1894-1899, 2017 02 08.
Artigo em Inglês | MEDLINE | ID: mdl-28135083

RESUMO

Ultrafast, polarization-selective time-resolved X-ray absorption near-edge structure (XANES) was used to characterize the photochemistry of vitamin B12, cyanocobalamin (CNCbl), in solution. Cobalamins are important biological cofactors involved in methyl transfer, radical rearrangement, and light-activated gene regulation, while also holding promise as light-activated agents for spatiotemporal controlled delivery of therapeutics. We introduce polarized femtosecond XANES, combined with UV-visible spectroscopy, to reveal sequential structural evolution of CNCbl in the excited electronic state. Femtosecond polarized XANES provides the crucial structural dynamics link between computed potential energy surfaces and optical transient absorption spectroscopy. Polarization selectivity can be used to uniquely identify electronic contributions and structural changes, even in isotropic samples when well-defined electronic transitions are excited. Our XANES measurements reveal that the structural changes upon photoexcitation occur mainly in the axial direction, where elongation of the axial Co-CN bond and Co-NIm bond on a 110 fs time scale is followed by corrin ring relaxation on a 260 fs time scale. These observations expose features of the potential energy surfaces controlling cobalamin reactivity and deactivation.


Assuntos
Vitamina B 12/química , Estrutura Molecular , Processos Fotoquímicos , Fatores de Tempo , Espectroscopia por Absorção de Raios X , Raios X
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