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1.
JCEM Case Rep ; 2(5): luae047, 2024 May.
Artículo en Inglés | MEDLINE | ID: mdl-38660486

RESUMEN

Pituitary carcinomas are rare but associated with significant morbidity and mortality. They remain challenging to diagnose and manage. In this case, we describe a 56-year-old man who presented with erectile dysfunction and binocular vertical diplopia. He had central hypogonadism, secondary adrenal insufficiency, and central hypothyroidism on biochemical testing. His serum prolactin was 1517 mcg/L (1517 ng/mL; reference range 4-15 mcg/L), and his sellar magnetic resonance imaging showed a 2.0 × 2.2 × 3.1 cm pituitary tumor. Pathology revealed a prolactin-secreting carcinoma. Despite treatment with a high-dose dopaminergic, 2 transsphenoidal resections, and 1 course of radiation, prolactin levels continued to rise. He developed metastases to the epidural space and thecal sac from the thoracic to sacral spine, for which he received 12 cycles of temozolomide chemotherapy with initial clinical and biochemical response. This was followed by disease escape and progression. We discuss the clinical and imaging features that warrant a high index of suspicion for pituitary carcinoma and review contemporary treatment.

2.
J Med Microbiol ; 73(2)2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38415707

RESUMEN

Background. A bloodstream infection (BSI) presents a complex and serious health problem, a problem that is being exacerbated by increasing antimicrobial resistance (AMR).Gap Statement. The current turnaround times (TATs) for most antimicrobial susceptibility testing (AST) methods offer results retrospective of treatment decisions, and this limits the impact AST can have on antibiotic prescribing and patient care. Progress must be made towards rapid BSI diagnosis and AST to improve antimicrobial stewardship and reduce preventable deaths from BSIs. To support the successful implementation of rapid AST (rAST) in hospital settings, a rAST method that is affordable, is sustainable and offers comprehensive AMR detection is needed.Aim. To evaluate a scattered light-integrated collection (SLIC) device against standard of care (SOC) to determine whether SLIC could accelerate the current TATs with actionable, accurate rAST results for Gram-negative BSIs.Methods. Positive blood cultures from a tertiary referral hospital were studied prospectively. Flagged positive Gram-negative blood cultures were confirmed by Gram staining and analysed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Vitek 2, disc diffusion (ceftriaxone susceptibility only) and an SLIC device. Susceptibility to a panel of five antibiotics, as defined by European Committee on Antimicrobial Susceptibility Testing breakpoints, was examined using SLIC.Results. A total of 505 bacterial-antimicrobial combinations were analysed. A categorical agreement of 95.5 % (482/505) was achieved between SLIC and SOC. The 23 discrepancies that occurred were further investigated by the broth microdilution method, with 10 AST results in agreement with SLIC and 13 in agreement with SOC. The mean time for AST was 10.53±0.46 h and 1.94±0.02 h for Vitek 2 and SLIC, respectively. SLIC saved 23.96±1.47 h from positive blood culture to AST result.Conclusion. SLIC has the capacity to provide accurate AST 1 day earlier from flagged positive blood cultures than SOC. This significant time saving could accelerate time to optimal antimicrobial therapy, improving antimicrobial stewardship and management of BSIs.


Asunto(s)
Programas de Optimización del Uso de los Antimicrobianos , Sepsis , Humanos , Cultivo de Sangre , Estudios Retrospectivos , Bacterias Gramnegativas , Antibacterianos/farmacología
3.
Photochem Photobiol ; 100(1): 137-145, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-37029739

RESUMEN

Far-UVC, from filtered Krypton-Chloride lamps, is promising for reducing airborne transmission of disease. While significant research has been undertaken to investigate skin safety of these lamps, less work has been undertaken on eye safety. There is limited data on human eye safety or discomfort from the deployment of this germicidal technology. In this pilot study, immediate and delayed eye discomfort were assessed in a simulated office environment with deployment of Krypton-Chloride lamps, located on the ceiling and directed downwards into the occupied room. Discomfort was assessed immediately postexposure and several days after exposure using validated, Standard Patient Evaluation Eye Dryness (SPEED) and Ocular Surface Disease Index (OSDI) questionnaires. Our results show no significant eye discomfort or adverse effects from the deployment of Far-UVC in this simulated office environment, even when lamps were operated continuously with participants receiving head exposures of up to 50 mJ cm-2 . In addition, a statistically significant reduction in bacteria and fungi of 52% was observed. Far-UVC in this simulated office environment did not cause any clinically significant eye discomfort and was effective at reducing pathogens in the room. These results contribute an important step to further investigation of the interaction of Far-UVC with the human eye.


Asunto(s)
Cloruros , Rayos Ultravioleta , Humanos , Criptón , Proyectos Piloto , Piel/microbiología , Desinfección/métodos
5.
Biomedicines ; 11(10)2023 Oct 18.
Artículo en Inglés | MEDLINE | ID: mdl-37893192

RESUMEN

Introduction: The ferritin-lymphocyte ratio (FLR) is a novel inflammatory biomarker for the assessment of acute COVID-19 patients. However, the prognostic value of FLR for predicting adverse clinical outcomes in COVID-19 remains unclear, which hinders its clinical translation. Methods: We characterised the prognostic value of FLR in COVID-19 patients, as compared to established inflammatory markers. Results: In 217 study patients (69 years [IQR: 55-82]; 60% males), FLR was weakly correlated with CRP (R = 0.108, p = 0.115) and white cell count (R = -0.144; p = 0.034). On ROC analysis, an FLR cut-off of 286 achieved a sensitivity of 86% and a specificity of 30% for predicting inpatient mortality (AUC 0.60, 95% CI: 0.53-0.67). The negative predictive values of FLR for ruling out mortality, non-invasive ventilation requirement and critical illness (intubation and/or ICU admission) were 86%, 85% and 93%, respectively. FLR performed similarly to CRP (AUC 0.60 vs. 0.64; p = 0.375) for predicting mortality, but worse than CRP for predicting non-fatal outcomes (all p < 0.05). On Kaplan-Meier analysis, COVID-19 patients with FLR values > 286 had worse inpatient survival than patients with FLR ≤ 286, p = 0.041. Conclusions: FLR has prognostic value in COVID-19 patients, and appears unrelated to other inflammatory markers such as CRP and WCC. FLR exhibits high sensitivity and negative predictive values for adverse clinical outcomes in COVID-19, and may be a good "rule-out" test. Further work is needed to improve the sensitivity of FLR and validate its role in prospective studies for guiding clinical management.

6.
Biomedicines ; 11(9)2023 Aug 30.
Artículo en Inglés | MEDLINE | ID: mdl-37760863

RESUMEN

Background: CRB-65 (Confusion; Respiratory rate ≥ 30/min; Blood pressure ≤ 90/60 mmHg; age ≥ 65 years) is a risk score for prognosticating patients with COVID-19 pneumonia. However, a significant proportion of COVID-19 patients have normal chest X-rays (CXRs). The influence of CXR abnormalities on the prognostic value of CRB-65 is unknown, limiting its wider applicability. Methods: We assessed the influence of CXR abnormalities on the prognostic value of CRB-65 in COVID-19. Results: In 589 study patients (71 years (IQR: 57-83); 57% males), 186 (32%) had normal CXRs. On ROC analysis, CRB-65 performed similarly in patients with normal vs. abnormal CXRs for predicting inpatient mortality (AUC 0.67 ± 0.05 vs. 0.69 ± 0.03). In patients with normal CXRs, a CRB-65 of 0 ruled out mortality, NIV requirement and critical illness (intubation and/or ICU admission) with negative predictive values (NPVs) of 94%, 98% and 99%, respectively. In patients with abnormal CXRs, a CRB-65 of 0 ruled out the same endpoints with NPVs of 91%, 83% and 86%, respectively. Patients with low CRB-65 scores had better inpatient survival than patients with high CRB-65 scores, irrespective of CXR abnormalities (all p < 0.05). Conclusions: CRB-65, CXR and CRP are independent predictors of mortality in COVID-19. Adding CXR findings (dichotomised to either normal or abnormal) to CRB-65 does not improve its prognostic accuracy. A low CRB-65 score of 0 may be a good rule-out test for adverse clinical outcomes in COVID-19 patients with normal or abnormal CXRs, which deserves prospective validation.

7.
Mol Pharm ; 20(10): 5019-5031, 2023 Oct 02.
Artículo en Inglés | MEDLINE | ID: mdl-37682633

RESUMEN

Grid-based systematic search methods are used to investigate molecule-molecule, molecule-surface, and surface-surface contributions to interparticle interactions in order to identify the crystal faces that most strongly affect particle behavior during powder blend formulation and delivery processes. The model system comprises terbutaline sulfate (TBS) as an active pharmaceutical ingredient (API) and α-form lactose monohydrate (LMH). A combination of systematic molecular modeling and X-ray computed tomography (XCT) is used to determine not only the adhesive and cohesive interparticle energies but, also the agglomeration behavior during manufacturing and de-agglomeration behavior during delivery after inhalation. This is achieved through a detailed examination of the balance between the adhesive and cohesive energies with the XCT results confirming the blend segregation tendencies, through the particle-particle de-agglomeration process. The results reveal that the cohesive interaction energies of TBS-TBS are higher than the adhesive energies between TBS and LMH, but that the cohesive energies of LMH-LMH are the smallest between molecule and molecule, molecule and surface, and surface and surface. This shows how systematic grid-search molecular modeling along with XCT can guide the digital formulation design of inhalation powders in order to achieve optimum aerosolization and efficacy for inhaled medicines. This will lead to faster pharmaceutical design with less variability, higher quality, and enhanced performance.

8.
bioRxiv ; 2023 Aug 09.
Artículo en Inglés | MEDLINE | ID: mdl-37609196

RESUMEN

The role of non-coding regulatory elements and how they might contribute to tissue type specificity of disease phenotypes is poorly understood. Autosomal Dominant Leukodystrophy (ADLD) is a fatal, adult-onset, neurological disorder that is characterized by extensive CNS demyelination. Most cases of ADLD are caused by tandem genomic duplications involving the lamin B1 gene ( LMNB1 ) while a small subset are caused by genomic deletions upstream of the gene. Utilizing data from recently identified families that carry LMNB1 gene duplications but do not exhibit demyelination, ADLD patient tissues, CRISPR modified cell lines and mouse models, we have identified a novel silencer element that is lost in ADLD patients and that specifically targets overexpression to oligodendrocytes. This element consists of CTCF binding sites that mediate three-dimensional chromatin looping involving the LMNB1 and the recruitment of the PRC2 repressor complex. Loss of the silencer element in ADLD identifies a previously unknown role for silencer elements in tissue specificity and disease causation.

10.
Data Brief ; 50: 109485, 2023 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-37645445

RESUMEN

Detailed atomistic interactions of 1,1,1,2-tetrafluoroethane (HFA-134a) liquid were presented in a data format, namely, DL_ANALYSER Notation for Atomic Interactions (DANAI), that annotates precisely the nature of interactions that is discoverable and searchable without having to resolve to diagrammatic illustrations. The datasets were obtained from raw atomic trajectory files of HFA-134a pure liquid models produced by using DL_POLY molecular dynamics software package. The trajectory datafiles contain expressions of atomic species in a natural chemical sense, and hence, provide localized key interactions, 'at a glance', of the liquid model on otherwise a typically disordered system consists of complex network of intermolecular interactions. The data provide insights to detailed structural behavior of molecules in liquid phase, and can be used as cheminformatics comparative investigations, linking to other molecular system models that contain similar interaction types and chemical species. This can form the foundation of investigations into the role of HFA-134a plays within different applications. For example, it can be used to compare structural and atomic interaction differences with alternative refrigerants, or as liquid propellants in pharmaceutical devices when solvating formulation ingredients.

11.
J Pers Med ; 13(6)2023 May 29.
Artículo en Inglés | MEDLINE | ID: mdl-37373898

RESUMEN

Background: In COVID-19 patients, lymphocyte-CRP ratio (LCR) is a promising biomarker for predicting adverse clinical outcomes. How well LCR performs compared to conventional inflammatory markers for prognosticating COVID-19 patients remains unclear, which hinders the clinical translation of this novel biomarker. Methods: In a cohort of COVID-19 inpatients, we characterised the clinical applicability of LCR by comparing its prognostic value against conventional inflammatory markers for predicting inpatient mortality and a composite of mortality, invasive/non-invasive ventilation and intensive care unit admissions. Results: Of the 413 COVID-19 patients, 100 (24%) patients suffered inpatient mortality. On Receiver Operating Characteristics analysis, LCR performed similarly to CRP for predicting mortality (AUC 0.74 vs. 0.71, p = 0.049) and the composite endpoint (AUC 0.76 vs. 0.76, p = 0.812). LCR outperformed lymphocyte counts (AUC 0.74 vs. 0.66, p = 0.002), platelet counts (AUC 0.74 vs. 0.61, p = 0.003) and white cell counts (AUC 0.74 vs. 0.54, p < 0.001) for predicting mortality. On Kaplan-Meier analysis, patients with a low LCR (below a 58 cut-off) had worse inpatient survival than patients with other LCR values (p < 0.001). Conclusion: LCR appears comparable to CRP, but outperformed other inflammatory markers, for prognosticating COVID-19 patients. Further studies are required to improve the diagnostic value of LCR to facilitate clinical translation.

12.
PLoS One ; 18(4): e0284523, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37083886

RESUMEN

INTRODUCTION: Assessment of inpatient mortality risk in COVID-19 patients is important for guiding clinical decision-making. High sensitivity cardiac troponin T (hs-cTnT) is a biomarker of cardiac injury associated with a worse prognosis in COVID-19. We explored how hs-cTnT could potentially be used in clinical practice for ruling in and ruling out mortality in COVID-19. METHOD: We tested the diagnostic value of hs-cTnT in laboratory-confirmed COVID-19 patients (≥18 years old) admitted to the Royal Berkshire Hospital (UK) between 1st March and 10th May 2020. A normal hs-cTnT was defined as a value within the 99th percentile of healthy individuals (≤14 ng/L), and an elevated hs-cTnT was defined as >14 ng/L. Adverse clinical outcome was defined as inpatient mortality related to COVID-19. RESULTS: A total of 191 COVID-19 patients (62% male; age 66±16 years) had hs-cTnT measured on admission. Of these patients, 124 (65%) had elevated hs-cTnT and 67 (35%) had normal hs-cTnT. On a group level, patients with elevated hs-cTnT had worse inpatient survival (p = 0.0014; Kaplan-Meier analysis) and higher risk of inpatient mortality (HR 5.84 [95% CI 1.29-26.4]; p = 0.02; Cox multivariate regression) compared to patients with normal hs-cTnT. On a per-patient level, a normal hs-cTnT had a negative predictive value of 94% (95% CI: 85-98%) for ruling out mortality, whilst an elevated hs-cTnT had a low positive predictive value of 38% (95% CI: 39-47%) for ruling in mortality. CONCLUSIONS: In this study cohort of COVID-19 patients, the potential clinical utility of hs-cTnT appears to rest in ruling out inpatient mortality. This finding, if prospectively validated in a larger study, may allow hs-cTnT to become an important biomarker to facilitate admission-avoidance and early safe discharge.


Asunto(s)
COVID-19 , Troponina , Humanos , Masculino , Persona de Mediana Edad , Anciano , Anciano de 80 o más Años , Adolescente , Femenino , Pacientes Internos , COVID-19/diagnóstico , Biomarcadores , Pronóstico , Troponina T
13.
J Intern Med ; 294(1): 21-46, 2023 07.
Artículo en Inglés | MEDLINE | ID: mdl-37106509

RESUMEN

In acute coronavirus disease 19 (COVID-19) patients, effective clinical risk stratification has important implications on treatment and therapeutic resource distribution. This article reviews the evidence behind a wide range of biomarkers with prognostic value in COVID-19. Patient characteristics and co-morbidities, such as cardiovascular and respiratory diseases, are associated with increased mortality risk. Peripheral oxygen saturation and arterial oxygenation are predictive of severe respiratory compromise, whereas risk scores such as the 4C-score enable multi-factorial prognostic risk estimation. Blood tests such as markers of inflammation, cardiac injury and d-dimer and abnormalities on electrocardiogram are linked to inpatient prognosis. Of the imaging modalities, lung ultrasound and echocardiography enable the bedside assessment of prognostic abnormalities in COVID-19. Chest radiograph (CXR) and computed tomography (CT) can inform about prognostic pulmonary pathologies, whereas cardiovascular CT detects high-risk features such as coronary artery and aortic calcification. Dynamic changes in biomarkers, such as blood tests, CXR, CT and electrocardiogram findings, can further inform about disease severity and prognosis. Despite the vast volumes of existing evidence, several gaps exist in our understanding of COVID-19 biomarkers. First, the pathophysiological basis on which these markers can foretell prognosis in COVID-19 remains poorly understood. Second, certain under-explored tests such as thoracic impedance assessment and cardiovascular magnetic resonance imaging deserve further investigation. Lastly, the prognostic values of most biomarkers in COVID-19 are derived from retrospective analyses. Prospective studies are required to validate these markers for guiding clinical decision-making and to facilitate their translation into clinical management pathways.


Asunto(s)
COVID-19 , Humanos , Pronóstico , Estudios Retrospectivos , Biomarcadores , Medición de Riesgo
14.
J Neuropathol Exp Neurol ; 82(4): 296-301, 2023 03 20.
Artículo en Inglés | MEDLINE | ID: mdl-36718578

RESUMEN

The COVID-19 pandemic has had a significant impact on medical services. Many countries postponed nonemergent procedures to preserve hospital resources for the unprecedented situation. Surgical backlogs caused by the COVID-19 pandemic have been evaluated by different groups. However, the impact of this pandemic on pathology and specifically neuropathology (NP) services has received limited attention. In this study, we reviewed all NP reports of the London Health Sciences Centre from January 2018 (2 years before the pandemic declaration) until the end of the year 2021. Demographic information and pathology details were collected. For tumors, site, histopathology types, and WHO grading were analyzed. In nontumoral specimens, pathological diagnoses were compared in pre- and postpandemic time. The total number of NP samples reached its lowest in April 2020, corresponding to the first Ontario provincial lockdown, and fluctuated throughout the studied period. Among the different types of NP surgical specimens, muscle and epilepsy-related specimens showed a more significant reduction, compared to neoplastic specimens. In 2020, the proportion of tumor specimens from patients older than 40 years of age increased. Similarly, the proportion of high-grade glioma and brain metastasis diagnoses also increased. Lastly, we observed a marked increase in biopsies for temporal arteritis and other inflammatory lesions.


Asunto(s)
COVID-19 , Humanos , Canadá/epidemiología , Control de Enfermedades Transmisibles , Pandemias , Biopsia
16.
Brain Pathol ; 33(2): e13121, 2023 03.
Artículo en Inglés | MEDLINE | ID: mdl-36180818

RESUMEN

Patients with epilepsy are at elevated risk for premature mortality, of which sudden unexpected death in epilepsy (SUDEP) is one of the leading causes. SUDEP incidence varies significantly depending on the population and the methods used to document the cause of death. We performed retrospective case review at the London Health Sciences Centre for the period of 2000 to 2018. Clinical information, scene investigations, general pathology findings, toxicology, and neuropathology findings were obtained, examined, and confirmed by two neuropathologists and one epileptologist. The characteristics were compared and summarized. We also evaluated the impact of 2010 revision of Ontario Coroner Act Regulation, which significantly limited whole brain examination. Among the 12,206 cases reviewed, we identified 152 cases with a known history of epilepsy. Ninety-seven cases (64%) were classified as SUDEP. There were significantly more SUDEP decedents found dead unwitnessed at night in prone position, than non-SUDEP. Generalized seizures were strongly associated with SUDEP. A male predominance was observed in SUDEP group between 15 and 35 years old. Near half of the brains examined were "unremarkable." There was no difference in neuropathology findings between SUDEP and non-SUDEP groups. After implementation of the 2010 revision of Ontario Coroner Act Regulation, fixed whole brain examination was reduced from 88% to 7% of the epilepsy-related death investigation. Except a lower diagnosis rate of "inflammatory/infectious changes," there were no significant differences in neuropathology findings. This is the first detailed clinical-pathological study on epilepsy-related death based on a Canadian cohort. This study reinforces the previously reported findings in SUDEP and highlights the importance of clinicopathological correlation for accurate classification of epilepsy-related death.


Asunto(s)
Epilepsia , Muerte Súbita e Inesperada en la Epilepsia , Humanos , Masculino , Adolescente , Adulto Joven , Adulto , Femenino , Estudios Retrospectivos , Ontario/epidemiología , Correlación de Datos , Epilepsia/epidemiología , Convulsiones/complicaciones , Muerte Súbita/epidemiología , Muerte Súbita/etiología , Factores de Riesgo
17.
Sci Rep ; 12(1): 19393, 2022 11 12.
Artículo en Inglés | MEDLINE | ID: mdl-36371444

RESUMEN

Understanding the response of bacteria to environmental stress is hampered by the relative insensitivity of methods to detect growth. This means studies of antibiotic resistance and other physiological methods often take 24 h or longer. We developed and tested a scattered light and detection system (SLIC) to address this challenge, establishing the limit of detection, and time to positive detection of the growth of small inocula. We compared the light-scattering of bacteria grown in varying high and low nutrient liquid medium and the growth dynamics of two closely related organisms. Scattering data was modelled using Gompertz and Broken Stick equations. Bacteria were also exposed meropenem, gentamicin and cefoxitin at a range of concentrations and light scattering of the liquid culture was captured in real-time. We established the limit of detection for SLIC to be between 10 and 100 cfu mL-1 in a volume of 1-2 mL. Quantitative measurement of the different nutrient effects on bacteria were obtained in less than four hours and it was possible to distinguish differences in the growth dynamics of Klebsiella pneumoniae 1705 possessing the BlaKPC betalactamase vs. strain 1706 very rapidly. There was a dose dependent difference in the speed of action of each antibiotic tested at supra-MIC concentrations. The lethal effect of gentamicin and lytic effect of meropenem, and slow bactericidal effect of cefoxitin were demonstrated in real time. Significantly, strains that were sensitive to antibiotics could be identified in seconds. This research demonstrates the critical importance of improving the sensitivity of bacterial detection. This results in more rapid assessment of susceptibility and the ability to capture a wealth of data on the growth dynamics of bacteria. The rapid rate at which killing occurs at supra-MIC concentrations, an important finding that needs to be incorporated into pharmacokinetic and pharmacodynamic models. Importantly, enhanced sensitivity of bacterial detection opens the possibility of susceptibility results being reportable clinically in a few minutes, as we have demonstrated.


Asunto(s)
Antibacterianos , Cefoxitina , Antibacterianos/farmacocinética , Meropenem/farmacología , Cefoxitina/farmacología , Klebsiella pneumoniae , Gentamicinas/farmacología , Pruebas de Sensibilidad Microbiana
18.
Cryst Growth Des ; 22(5): 3042-3059, 2022 May 04.
Artículo en Inglés | MEDLINE | ID: mdl-35529067

RESUMEN

The solvent-mediated crystal morphologies of the α and ß polymorphic forms of l-glutamic acid are presented. This work applies a digital mechanistically based workflow that encompasses calculation of the crystal lattice energy and its constituent intermolecular synthons, their interaction energies, and their key role in understanding and predicting crystal morphology as well as assessing the surface chemistry, topology, and solvent binding on crystal habit growth surfaces. Through a comparison between the contrasting morphologies of the conformational polymorphs of l-glutamic acid, this approach highlights how the interfacial chemistry of organic crystalline materials and their inherent anisotropic interactions with their solvation environments direct their crystal habit with potential impact on their further downstream processing behavior.

19.
Genome Biol Evol ; 14(5)2022 05 03.
Artículo en Inglés | MEDLINE | ID: mdl-35510983

RESUMEN

Ants, bees, wasps, bark beetles, and other species have haploid males and diploid females. Although such haplodiploid species play key ecological roles and are threatened by environmental changes, no general framework exists for simulating their genetic evolution. Here, we use the SLiM simulation environment to build a novel model for individual-based forward simulation of genetic evolution in haplodiploids. We compare the fates of adaptive and deleterious mutations and find that selection on recessive mutations is more effective in haplodiploids than in diploids. Our open-source model will foster an understanding of the evolution of sociality and how ecologically important haplodiploid species may respond to changing environments.


Asunto(s)
Diploidia , Avispas , Animales , Abejas/genética , Evolución Biológica , Evolución Molecular , Femenino , Genoma , Haploidia , Masculino , Avispas/genética
20.
Faraday Discuss ; 235(0): 467-489, 2022 07 14.
Artículo en Inglés | MEDLINE | ID: mdl-35389403

RESUMEN

Para amino benzoic acid (PABA) has two well-characterised α- and ß-polymorphic forms and, whilst both crystallise in the monoclinic space group P21/n, they have quite different crystal chemistry and crystallisability behaviour. Previous work has shown that the molecular conformation deformation energy in the crystalline state is higher for the ß-form than for the α-form and that the lattice energy for the former converges more slowly than for the latter overall. This suggests that not only is there a higher barrier to crystallisation for the ß-form but also that low solution supersaturations might be needed for it to preferentially nucleate. Additionally, solute cluster propensity and solute solvation energetic analysis highlight the importance of an aqueous solvation environment in inhibiting the α-form's strong OH⋯O carboxylic acid hydrogen bond (H-bond) dimer. Despite this, the detailed molecular-scale pathway from solvated molecules to 3D crystallographic structure still remains unclear, most notably regarding how the nucleation process is activated and how, as a result, this mediates the preferential formation of either of the two polymorphic forms. Molecular dynamics (MD) simulations coupled with FTIR studies and intermolecular synthon analysis address this issue through characterisation of the propensity of the incipient bulk synthons that are important in the crystallisation of the two polymorphic forms within the solution state. MD molecular trajectory analysis within crystallisation solutions reveals a greater propensity for OH⋯O synthons (both single H-bonds and homodimers) typical of the α-form and NH⋯O synthons found in both the α- and ß-forms when compared to aqueous solution but much lower propensities for the ß-form's "fingerprinting" OH⋯N and π-π stacking synthons. In contrast, data from the aqueous solution environment reveals a much greater propensity for the ß-form's π-π interaction synthons. IR dilution studies in acetonitrile in the carbonyl region reveal the presence of two CO vibrational stretching bands, whose relative intensities vary as a function of solution dilution. These were assigned to the solvated PABA monomer and a COOH dimer of PABA. Similar data in ethanol shows a main CO stretching band with a shoulder peak suggesting a similar monomer vs. dimer speciation may exist in this solvent. The IR data is consistent with the organic solvent MD data, albeit the corresponding analysis for the aqueous solution was precluded due to the latter's strong OH vibrational mode which restricted validation in aqueous solutions.


Asunto(s)
Ácido 4-Aminobenzoico , Aminoácidos , Enlace de Hidrógeno , Conformación Molecular , Solventes/química , Agua/química
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