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The widely accepted existence of an inherent limit of atmospheric predictability is usually attributed to weather's sensitive dependence on initial conditions. This signature feature of chaos was first discovered in the Lorenz system, initially derived as a simplified model of thermal convection. In a recent study of a high-dimensional generalization of the Lorenz system, it was reported that the predictability of its chaotic solutions exhibits a non-monotonic dimensional dependence. Since raising the dimension of the Lorenz system is analogous to refining the model vertical resolution when viewed as a thermal convection model, it is questioned whether this non-monotonicity is also found in numerical weather prediction models. Predictability in the sense of sensitive dependence on initial conditions can be measured based on deviation time, that is, the time of threshold-exceeding deviations between the solutions with minute differences in initial conditions. Through ensemble experiments involving both the high-dimensional generalizations of the Lorenz system and real-case simulations by a numerical weather prediction model, this study demonstrates that predictability can depend non-monotonically on model vertical resolution. Further analysis shows that the spatial distribution of deviation time strongly contributes to this non-monotonicity. It is suggested that chaos, or sensitive dependence on initial conditions, leads to non-monotonic dependence on model vertical resolution of deviation time and, by extension, atmospheric predictability.
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The classic Lorenz equations were originally derived from the two-dimensional Rayleigh-Bénard convection system considering an idealized case with the lowest order of harmonics. Although the low-order Lorenz equations have traditionally served as a minimal model for chaotic and intermittent atmospheric motions, even the dynamics of the two-dimensional Rayleigh-Bénard convection system is not fully represented by the Lorenz equations, and such differences have yet to be clearly identified in a systematic manner. In this paper, the convection problem is revisited through an investigation of various dynamical behaviors exhibited by a two-dimensional direct numerical simulation (DNS) and the generalized expansion of the Lorenz equations (GELE) derived by considering additional higher-order harmonics in the spectral expansions of periodic solutions. Notably, GELE allows us to understand how nonlinear interactions among high-order modes alter the dynamical features of the Lorenz equations including fixed points, chaotic attractors, and periodic solutions. It is verified that numerical solutions of the DNS can be recovered from the solutions of GELE when we consider the system with sufficiently high-order harmonics. At the lowest order, the classic Lorenz equations are recovered from GELE. Unlike in the Lorenz equations, we observe limit tori, which are the multi-dimensional analog of limit cycles, in the solutions of the DNS and GELE at high orders. Initial condition dependency in the DNS and Lorenz equations is also discussed.
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The COVID-19 pandemic has prompted governments around the world to impose mitigation strategies of unprecedented scales, typically involving some form of restrictions on social activities and transportation. The South Korean government has been recommending a collection of guidelines now known as social distancing, leading to reduced human activities. This study analyzes changes in the concentrations of fine particulate matter (PM2.5) during the 30-day periods before and since the start of social distancing on 29 February 2020 using measurement data from air quality monitoring stations at various locations of the seven major cities of South Korea, namely, Seoul, Busan, Incheon, Daegu, Daejeon, Gwangju, and Ulsan. All seven cities experienced decreased levels of PM2.5 concentration by up to 25% and smaller fluctuations during the period of social distancing. Inter-city comparisons show that the PM2.5 concentration changes are positively correlated with the city-wide PM2.5 emission fractions for mobile sources and negatively correlated with the city-wide PM2.5 emission fractions for combustion and industrial process sources. In addition, the meteorological influences favorable for transboundary pollutant transport have weakened during the period under COVID-19 social distancing. Intra-city comparisons show that decreases in the intra-city variability of PM2.5 concentration were larger in coastal cities than in inland cities. Comparisons between the inter- and intra-city variabilities in the PM2.5 concentration changes under social distancing highlight the importance of taking into account intra-city variabilities in addition to inter-city variabilities.
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Seoul, the most populous city in South Korea, has been practicing social distancing to slow down the spread of coronavirus disease 2019 (COVID-19). Fine particulate matter (PM2.5) and other air pollutants measured in Seoul over the two 30 day periods before and after the start of social distancing are analyzed to assess the change in air quality during the period of social distancing. The 30 day mean PM2.5 concentration decreased by 10.4% in 2020, which is contrasted with an average increase of 23.7% over the corresponding periods in the previous 5 years. The PM2.5 concentration decrease was city-wide and more prominent during daytime than at nighttime. The concentrations of carbon monoxide (CO) and nitrogen dioxide (NO2) decreased by 16.9% and 16.4%, respectively. These results show that social distancing, a weaker forcing toward reduced human activity than a strict lockdown, can help lower pollutant emissions. At the same time, synoptic conditions and the decrease in aerosol optical depth over the regions to the west of Seoul support that the change in Seoul's air quality during the COVID-19 social distancing can be interpreted as having been affected by reductions in the long-range transport of air pollutants as well as local emission reductions.
Asunto(s)
Contaminación del Aire/análisis , Infecciones por Coronavirus/epidemiología , Monitoreo del Ambiente , Neumonía Viral/epidemiología , Contaminantes Atmosféricos/análisis , Betacoronavirus , COVID-19 , Humanos , Pandemias , Material Particulado/análisis , SARS-CoV-2 , SeúlRESUMEN
The Lorenz system is a simplified model of Rayleigh-Bénard convection, a thermally driven fluid convection between two parallel plates. Two additional physical ingredients are considered in the governing equations, namely, rotation of the model frame and the presence of a density-affecting scalar in the fluid, in order to derive a six-dimensional nonlinear ordinary differential equation system. Since the new system is an extension of the original three-dimensional Lorenz system, the behavior of the new system is compared with that of the old system. Clear shifts of notable bifurcation points in the thermal Rayleigh parameter space are seen in association with the extension of the Lorenz system, and the range of thermal Rayleigh parameters within which chaotic, periodic, and intermittent solutions appear gets elongated under a greater influence of the newly introduced parameters. When considered separately, the effects of scalar and rotation manifest differently in the numerical solutions; while an increase in the rotational parameter sharply neutralizes chaos and instability, an increase in a scalar-related parameter leads to the rise of a new type of chaotic attractor. The new six-dimensional system is found to self-synchronize, and surprisingly, the transfer of solutions to only one of the variables is needed for self-synchronization to occur.
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AGS-16C3F is an antibody-drug conjugate (ADC) against ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3) containing the mcMMAF linker-payload currently in development for treatment of metastatic renal cell carcinoma. AGS-16C3F and other ADCs have been reported to cause ocular toxicity in patients by unknown mechanisms. To investigate this toxicity, we developed an in vitro assay using human corneal epithelial cells (HCEC) and show that HCECs internalized AGS-16C3F and other ADCs by macropinocytosis, causing inhibition of cell proliferation. We observed the same mechanism for target-independent internalization of AGS-16C3F in fibroblasts and human umbilical vein endothelial cells (HUVEC). Macropinocytosis-mediated intake of macromolecules is facilitated by the presence of positive charges or hydrophobic residues on the surface of the macromolecule. Modification of AGS-16C3F, either by attachment of poly-glutamate peptides, mutation of residue K16 to D on AGS-16C3F [AGS-16C3F(K16D)], or decreasing the overall hydrophobicity via attachment of polyethylene glycol moieties, significantly reduced cytotoxicity against HCECs and other primary cells. Rabbits treated with AGS-16C3F showed significant ocular toxicity, whereas those treated with AGS-16C3F(K16D) presented with less severe and delayed toxicities. Both molecules displayed similar antitumor activity in a mouse xenograft model. These findings establish a mechanism of action for target-independent toxicities of AGS-16C3F and ADCs in general, and provide methods to ameliorate these toxicities.Significance: These findings reveal a mechanism for nonreceptor-mediated toxicities of antibody drug conjugates and potential solutions to alleviate these toxicities. Cancer Res; 78(8); 2115-26. ©2018 AACR.
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Anticuerpos Monoclonales Humanizados/farmacología , Epitelio Corneal/efectos de los fármacos , Inmunoconjugados/toxicidad , Pinocitosis/efectos de los fármacos , Secuencia de Aminoácidos , Animales , Anticuerpos Monoclonales Humanizados/uso terapéutico , Células Cultivadas , Células Endoteliales de la Vena Umbilical Humana , Humanos , Macaca fascicularis , Masculino , Modelos Animales , Conejos , Homología de Secuencia de AminoácidoRESUMEN
CD37 is a tetraspanin expressed on malignant B cells. Recently, CD37 has gained interest as a therapeutic target. We developed AGS67E, an antibody-drug conjugate that targets CD37 for the potential treatment of B/T-cell malignancies. It is a fully human monoclonal IgG2 antibody (AGS67C) conjugated, via a protease-cleavable linker, to the microtubule-disrupting agent monomethyl auristatin E (MMAE). AGS67E induces potent cytotoxicity, apoptosis, and cell-cycle alterations in many non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL) cell lines and patient-derived samples in vitro. It also shows potent antitumor activity in NHL and CLL xenografts, including Rituxan-refractory models. During profiling studies to confirm the reported expression of CD37 in normal tissues and B-cell malignancies, we made the novel discovery that the CD37 protein was expressed in T-cell lymphomas and in AML. AGS67E bound to >80% of NHL and T-cell lymphomas, 100% of CLL and 100% of AML patient-derived samples, including CD34(+)CD38(-) leukemic stem cells. It also induced cytotoxicity, apoptosis, and cell-cycle alterations in AML cell lines and antitumor efficacy in orthotopic AML xenografts. Taken together, this study shows not only that AGS67E may serve as a potential therapeutic for B/T-cell malignancies, but it also demonstrates, for the first time, that CD37 is well expressed and a potential drug target in AML.
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Anticuerpos Monoclonales/farmacología , Antígenos de Neoplasias/inmunología , Inmunoconjugados/farmacología , Leucemia Mieloide/tratamiento farmacológico , Linfoma no Hodgkin/tratamiento farmacológico , Tetraspaninas/inmunología , Ensayos Antitumor por Modelo de Xenoinjerto , Enfermedad Aguda , Animales , Anticuerpos Monoclonales/inmunología , Anticuerpos Monoclonales Humanizados , Citotoxicidad Celular Dependiente de Anticuerpos/efectos de los fármacos , Antígenos de Neoplasias/metabolismo , Apoptosis/efectos de los fármacos , Ciclo Celular/efectos de los fármacos , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Femenino , Humanos , Inmunoconjugados/inmunología , Leucemia Mieloide/inmunología , Leucemia Mieloide/metabolismo , Linfoma de Células B/tratamiento farmacológico , Linfoma de Células B/inmunología , Linfoma de Células B/metabolismo , Linfoma no Hodgkin/inmunología , Linfoma no Hodgkin/metabolismo , Linfoma de Células T/tratamiento farmacológico , Linfoma de Células T/inmunología , Linfoma de Células T/metabolismo , Ratones Endogámicos NOD , Ratones SCID , Oligopéptidos/inmunología , Oligopéptidos/metabolismo , Tetraspaninas/metabolismo , Resultado del Tratamiento , Carga Tumoral/efectos de los fármacos , Células Tumorales CultivadasRESUMEN
Antibody drug conjugates (ADCs) are monoclonal antibodies designed to deliver a cytotoxic drug selectively to antigen expressing cells. Several components of an ADC including the selection of the antibody, the linker, the cytotoxic drug payload and the site of attachment used to attach the drug to the antibody are critical to the activity and development of the ADC. The cytotoxic drugs or payloads used to make ADCs are typically conjugated to the antibody through cysteine or lysine residues. This results in ADCs that have a heterogeneous number of drugs per antibody. The number of drugs per antibody commonly referred to as the drug to antibody ratio (DAR), can vary between 0 and 8 drugs for a IgG1 antibody. Antibodies with 0 drugs are ineffective and compete with the ADC for binding to the antigen expressing cells. Antibodies with 8 drugs per antibody have reduced in vivo stability, which may contribute to non target related toxicities. In these studies we incorporated a non-natural amino acid, para acetyl phenylalanine, at two unique sites within an antibody against Her2/neu. We covalently attached a cytotoxic drug to these sites to form an ADC which contains two drugs per antibody. We report the results from the first direct preclinical comparison of a site specific non-natural amino acid anti-Her2 ADC and a cysteine conjugated anti-Her2 ADC. We report that the site specific non-natural amino acid anti-Her2 ADCs have superior in vitro serum stability and preclinical toxicology profile in rats as compared to the cysteine conjugated anti-Her2 ADCs. We also demonstrate that the site specific non-natural amino acid anti-Her2 ADCs maintain their in vitro potency and in vivo efficacy against Her2 expressing human tumor cell lines. Our data suggests that site specific non-natural amino acid ADCs may have a superior therapeutic window than cysteine conjugated ADCs.
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Anticuerpos Monoclonales Humanizados/química , Antineoplásicos/química , Cisteína/química , Inmunoconjugados/química , Animales , Sitios de Unión , Línea Celular Tumoral , Estabilidad de Medicamentos , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Inmunoconjugados/sangre , Inmunoconjugados/farmacocinética , Inmunoconjugados/farmacología , Masculino , Ratones , Ratas , Receptor ErbB-2/metabolismo , Albúmina Sérica/metabolismo , Especificidad por Sustrato , Trastuzumab , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
(S)-2-hydroxypropylphosphonate ((S)-2-HPP) epoxidase (HppE) is a mononuclear non-haem-iron-dependent enzyme responsible for the final step in the biosynthesis of the clinically useful antibiotic fosfomycin. Enzymes of this class typically catalyse oxygenation reactions that proceed via the formation of substrate radical intermediates. By contrast, HppE catalyses an unusual dehydrogenation reaction while converting the secondary alcohol of (S)-2-HPP to the epoxide ring of fosfomycin. Here we show that HppE also catalyses a biologically unprecedented 1,2-phosphono migration with the alternative substrate (R)-1-HPP. This transformation probably involves an intermediary carbocation, based on observations with additional substrate analogues, such as (1R)-1-hydroxyl-2-aminopropylphosphonate, and model reactions for both radical- and carbocation-mediated migration. The ability of HppE to catalyse distinct reactions depending on the regio- and stereochemical properties of the substrate is given a structural basis using X-ray crystallography. These results provide compelling evidence for the formation of a substrate-derived cation intermediate in the catalytic cycle of a mononuclear non-haem-iron-dependent enzyme. The underlying chemistry of this unusual phosphono migration may represent a new paradigm for the in vivo construction of phosphonate-containing natural products that can be exploited for the preparation of new phosphonate derivatives.
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Biocatálisis , Fosfomicina/biosíntesis , Organofosfonatos/metabolismo , Oxidorreductasas/metabolismo , Productos Biológicos/química , Productos Biológicos/metabolismo , Cristalografía por Rayos X , Fosfomicina/química , Fosfomicina/metabolismo , Hidrogenación , Hierro , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Proteínas de Hierro no Heme/química , Proteínas de Hierro no Heme/metabolismo , Organofosfonatos/química , Oxidorreductasas/química , Especificidad por Sustrato , Factores de TiempoRESUMEN
PURPOSE: To improve the efficacy and reduce the gastrointestinal toxicity of the cancer prodrug, CPT-11, we have developed immunoconjugates of its active form, SN-38, and an anti-CEACAM5 antibody for targeted chemotherapy. EXPERIMENTAL DESIGN: SN-38 conjugates of the anti-CEACAM5 monoclonal antibody, labetuzumab (hMN-14), varying in the nature of the cross-linker attachment at the drug's 20-hydroxyl position, were evaluated in vitro, in metastatic and/or s.c. human colonic and pancreatic cancer xenografts in nude mice using appropriate controls, and in a CEACAM5-negative tumor model. RESULTS: A pilot study in a s.c. LS174T model of human colonic carcinoma established the relative effectiveness of different conjugates. In the lung metastatic model of GW-39 human colonic carcinoma in nude mice, therapy with two specific labetuzumab-SN-38 conjugates, using 0.25 mg SN-38 equivalent/kg, q4d x 8, significantly extended median survival time versus controls (P < 0.002). In an expanded evaluation in the s.c. LS174T xenograft model, specific SN-38 conjugates produced significant tumor growth control and increases in median survival time versus other controls, including CPT-11 at a 33-fold greater cumulative dose (P < 0.01). An improvement was also observed in the therapy of a s.c. human pancreatic tumor xenograft. In a CEACAM5-negative systemic lymphoma xenograft, one labetuzumab-SN-38 conjugate examined was ineffective, whereas the conjugate specific for the tumor model produced 100% survival. CONCLUSIONS: The promising labetuzumab-SN-38 conjugates developed showed selective therapeutic efficacy in human tumor models at nontoxic doses that were a fraction of the CPT-11 doses used.
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Anticuerpos Monoclonales/uso terapéutico , Camptotecina/análogos & derivados , Antígeno Carcinoembrionario/inmunología , Carcinoma/tratamiento farmacológico , Neoplasias del Colon/tratamiento farmacológico , Inmunoconjugados/uso terapéutico , Neoplasias Pancreáticas/tratamiento farmacológico , Animales , Anticuerpos Monoclonales/química , Anticuerpos Monoclonales Humanizados , Antineoplásicos/administración & dosificación , Antineoplásicos/uso terapéutico , Camptotecina/administración & dosificación , Camptotecina/química , Camptotecina/uso terapéutico , Carcinoma/inmunología , Neoplasias del Colon/inmunología , Sistemas de Liberación de Medicamentos/métodos , Femenino , Proteínas Ligadas a GPI , Humanos , Irinotecán , Ratones , Ratones Desnudos , Modelos Biológicos , Neoplasias Pancreáticas/inmunología , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
CPT-11 is a clinically used cancer drug, and it is a prodrug of the potent topoisomerase I inhibitor, SN-38 (7-ethyl-10-hydroxycamptothecin). To bypass the need for the in vivo conversion of CPT-11 and increase the therapeutic index, bifunctional derivatives of SN-38 were prepared for use in antibody-based targeted therapy of cancer. The general synthetic scheme incorporated an acetylene-azide click cycloaddition step in the design, a short polyethylene glycol spacer for aqueous solubility, and a maleimide group for conjugation. Conjugates of a humanized anti-CEACAM5 monoclonal antibody, hMN-14, prepared using these SN-38 derivatives were evaluated in vitro for stability in buffer and human serum and for antigen-binding and cytotoxicity in a human colon adenocarcinoma cell line. Conjugates of hMN-14 and SN-38 derivatives 16 and 17 were found promising for further development.
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Anticuerpos/química , Anticuerpos/inmunología , Antineoplásicos/síntesis química , Antineoplásicos/farmacología , Camptotecina/análogos & derivados , Acetileno/química , Antineoplásicos/química , Antineoplásicos/inmunología , Azidas/química , Camptotecina/síntesis química , Camptotecina/química , Camptotecina/farmacología , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Humanos , Irinotecán , Cinética , Estructura Molecular , Relación Estructura-ActividadRESUMEN
The final step in the biosynthesis of fosfomycin in Streptomyces wedmorensis is catalyzed by ( S)-2-hydroxypropylphosphonic acid (HPP) epoxidase ( Sw-HppE). A homologous enzyme from Pseudomonas syringae whose encoding gene ( orf3) shares a relatively low degree of sequence homology with the corresponding Sw-HppE gene has recently been isolated. This purified P. syringae protein was determined to catalyze the epoxidation of ( S)-HPP to fosfomycin and the oxidation of ( R)-HPP to 2-oxopropylphosphonic acid under the same conditions as Sw-HppE. Therefore, this protein is indeed a true HPP epoxidase and is termed Ps-HppE. Like Sw-HppE, Ps-HppE was determined to be post-translationally modified by the hydroxylation of a putative active site tyrosine (Tyr95). Analysis of the Fe(II) center by EPR spectroscopy using NO as a spin probe and molecular oxygen surrogate reveals that Ps-HppE's metal center is similar, but not identical, to that of Sw-HppE. The identity of the rate-determining step for the ( S)-HPP and ( R)-HPP reactions was determined by measuring primary deuterium kinetic effects, and the outcome of these results was correlated with density functional theory calculations. Interestingly, the reaction using the nonphysiological substrate ( R)-HPP was 1.9 times faster than that with ( S)-HPP for both Ps-HppE and Sw-HppE. This is likely due to the difference in bond dissociation energy of the abstracted hydrogen atom for each respective reaction. Thus, despite the low level of amino acid sequence identity, Ps-HppE is a close mimic of Sw-HppE, representing a second example of a non-heme iron-dependent enzyme capable of catalyzing dehydrogenation of a secondary alcohol to form a new C-O bond.
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Fosfomicina/biosíntesis , Oxidorreductasas/aislamiento & purificación , Oxidorreductasas/metabolismo , Pseudomonas syringae/enzimología , Secuencia de Aminoácidos , Clonación Molecular , Mononucleótido de Flavina/química , Mononucleótido de Flavina/metabolismo , Regulación Bacteriana de la Expresión Génica/fisiología , Hierro/química , Hierro/metabolismo , Datos de Secuencia Molecular , NAD/química , NAD/metabolismo , Oxidorreductasas/química , Oxígeno/química , Oxígeno/metabolismoRESUMEN
(S)-2-Hydroxypropylphosphonic acid epoxidase (HppE) is an O2-dependent, nonheme Fe(II)-containing oxidase that converts (S)-2-hydroxypropylphosphonic acid ((S)-HPP) to the regio- and enantiomerically specific epoxide, fosfomycin. Use of (R)-2-hydroxypropylphosphonic acid ((R)-HPP) yields the 2-keto-adduct rather than the epoxide. Here we report the chemical synthesis of a range of HPP analogues designed to probe the basis for this specificity. In past studies, NO has been used as an O2 surrogate to provide an EPR probe of the Fe(II) environment. These studies suggest that O2 binds to the iron, and substrates bind in a single orientation that strongly perturbs the iron environment. Recently, the X-ray crystal structure showed direct binding of the substrate to the iron, but both monodentate (via the phosphonate) and chelated (via the hydroxyl and phosphonate) orientations were observed. In the current study, hyperfine broadening of the homogeneous S = 3/2 EPR spectrum of the HppE-NO-HPP complex was observed when either the hydroxyl or the phosphonate group of HPP was enriched with 17O (I = 5/2). These results indicate that both functional groups of HPP bind to Fe(II) ion at the same time as NO, suggesting that the chelated substrate binding mode dominates in solution. (R)- and (S)-analogue compounds that maintained the core structure of HPP but added bulky terminal groups were turned over to give products analogous to those from (R)- and (S)-HPP, respectively. In contrast, substrate analogues lacking either the phosphonate or hydroxyl group were not turned over. Elongation of the carbon chain between the hydroxyl and phosphonate allowed binding to the iron in a variety of orientations to give keto and diol products at positions determined by the hydroxyl substituent, but no stable epoxide was formed. These studies show the importance of the Fe(II)-substrate chelate structure to active antibiotic formation. This fixed orientation may align the substrate next to the iron-bound activated oxygen species thought to mediate hydrogen atom abstraction from the nearest substrate carbon.