Search

Introduction. Vascular endothelial growth factor (VEGF), an angiogenic factor secreted by type II pneumocytes, could play a role in congenital diaphragmatic hernia (CDH) pathogenesis. Animal studies suggest that VEGF accelerates lung growth. Aim. To quantify VEGF on fetal lungs in a nitrofen rat model for CDH and to analyze the effect of tracheal occlusion (TO) in VEGF in fetal lung rats after nitrofen and in control rats not exposed to nitrofen. Methods. Pregnant rats received nitrofen on day 9.5 of gestation. Fetuses were divided into 2 groups: those that underwent TO on day 20 and those that did not. On day 21, fetuses were delivered, and the lungs were dissected for subsequent VEGF quantification. Results. CDH was detected in 43% of the fetuses that received nitrofen. Fetuses with CDH showed significantly reduced lung weight/fetal weight ratio and lower VEGF levels than the remainder. A higher VEGF value was observed after TO. Conclusions. VEGF protein was significantly lower in fetuses with CDH. TO induced a significant increase in VEGF compared to the fetuses that did not undergo TO. Although not statistically significant, we observed higher VEGF levels in fetuses with CDH and TO compared to fetuses with CDH and no further intervention.

The response to the special 2019 issue of Studia Gilsoniana on economics was so positive that it led to the creation of the Aquinas School of Leadership School of Economics (ASLSE). This 2021 publication is, therefore, a second special issue of Studia Gilsoniana on the same theme and the second installment of ASLSE’s economic journals. We are delighted to present here further fruits of thought from the maturing Studia Gilsoniana and ASLSE partnership. Economics is held to be a value-free, scientific enterprise, and as such there can be no relationship between economics and religion. Ayn Rand, a well-known novelist-turned-philosopher, took this position in an unapologetic way in her writings, specifically in her novel Atlas Shrugged. The contrary position to what we might call the Randian “strict separation” thesis holds that economics and religion are related, in some way and to some degree, and therefore should be considered in tandem. The papers in this special edition of Studia Gilsoniana set out to show the extent and quality of the relationship between economics and religion from a variety of viewpoints and historical periods.

This edition of Studia Gilsoniana inaugurates submission of articles on economic science based upon pre-modern principles of philosophy/science. Today, many journals address the intersection of economics and philosophy. Their contributors include practicing economists, economic historians, economist-philosophers, philosopher-economists, and economic methodologists. Research in this interdisciplinary field began to appear in the 1970s and later took shape in the 1980s with the appearance of its specialized academic journals. Today, the intersection of economics and philosophy is a vibrant area of inquiry and research. Books and journal pages are replete with references to classical philosophers such as Plato and Aristotle and their contributions to economic science. However, stronger connections need to be made related to the application of economic principles from the past to the present based upon enduring pre-modern principles of science. This is precisely what this inaugural issue celebrates.

The family Tymoviridae comprises positive-sense RNA viruses, which mainly infect plants. Recently, a few Tymoviridae -like viruses have been found in mosquitoes, which feed on vertebrate sources. We describe a novel Tymoviridae -like virus, putatively named, Guachaca virus (GUAV), isolated from Culex pipiens and Culex quinquefasciatus species of mosquitoes and collected in the rural area of Santa Marta, Colombia. After a cytopathic effect was observed in C6/36 cells, RNA was extracted and processed through the NetoVIR next-generation sequencing protocol, and data were analyzed through the VirMAP pipeline. Molecular and phenotypic characterization of the GUAV was achieved using a 5'/3' RACE, transmission electron microscopy, amplification in vertebrate cells, and phylogenetic analysis. A cytopathic effect was observed in C6/36 cells three days post-infection. The GUAV genome was successfully assembled, and its polyadenylated 3' end was corroborated. GUAV shared only 54.9% amino acid identity with its closest relative, Ek Balam virus , and was grouped with the latter and other unclassified insect-associated tymoviruses in a phylogenetic analysis. GUAV is a new member of a family previously described as comprising plant-infecting viruses, which seem to infect and replicate in mosquitoes. The sugar- and blood-feeding behavior of the Culex spp., implies a sustained contact with plants and vertebrates and justifies further studies to unravel the ecological scenario for transmission.

Guinea pigs (Cavia porcellus) have been reared for centuries in the Andean region for ceremonial purposes or as the main ingredient of traditional foods. The animals are kept in close proximity of households and interact closely with humans; this also occurs in western countries, where guinea pigs are considered pets. Even though it is acknowledged that domestic animals carry pathogenic yeasts in their tissues and organs that can cause human diseases, almost nothing is known in the case of guinea pigs. In this work we used traditional microbiological approaches and molecular biology techniques to isolate, identify, and characterize potentially zoonotic yeasts colonizing the nasal duct of guinea pigs raised as livestock in Southern Ecuador (Cañar Province). Our results show that 44% of the 100 animals studied were colonized in their nasal mucosa by at least eleven yeast species, belonging to eight genera: Wickerhamomyces, Diutina, Meyerozyma, Candida, Pichia, Rhodotorula, Galactomyces, and Cryptococcus. Noticeably, several isolates were insensitive toward several antifungal drugs of therapeutic use, including fluconazole, voriconazole, itraconazole, and caspofungin. Together, our results emphasize the threat posed by these potentially zoonotic yeasts to the farmers, their families, the final consumers, and, in general, to public and animal health.

Aedes aegypti is the primary vector of dengue, Zika, and chikungunya viruses. Studies have shown that insecticide resistance affects vector competence (VC) of some mosquito species. This study evaluates the effect of resistance to lambda-cyhalothrin and kdr V1016I mutation genotypes on the VC of Ae. aegypti strains for DENV-2, ZIKV, and CHIKV. Three Ae. aegypti strains with gradual lambda-cyhalothrin resistance (susceptible, resistant, and highly resistant) were infected with DENV-2, ZIKV, and CHIKV. Individual mosquitoes were tested to detect virus infection in the abdomen and head-salivary glands, using RT-PCR, and genotypes for V1016I mutations using allele-specific PCR. Recorded VC variables were midgut infection rate (MIR), dissemination rate (DIR), and dissemination efficiency (DIE). Lambda-cyhalothrin resistance affects differentially VC variables for ZIKV, DENV-2, and CHIKV. For ZIKV, an apparent gradual increase in DIR and DIE with the increase in insecticide resistance was observed. For DENV-2 the MIR and DIE were higher in insecticide resistant strains. For CHIKV, only MIR could be evaluated, this variable was higher in insecticide resistance strains. The presence of kdr V1016I mutation on mosquito resistant strains did not affect VC variables for three study viruses., Competing Interests: The authors have declared that no competing interest exist.

Introduction: Enteric viruses have been associated with the production of a variety of diseases transmitted by the fecal-oral route and carried through contaminated food and water. Given their structure and composition, they are highly resistant to environmental conditions and most of the chemical agents used in the purification processes. Therefore, the systematic monitoring of raw water is necessary to ensure its quality especially when it is used for producing drinking water for human consumption., Objective: We identified the presence of rotavirus and hepatitis A virus by means of the fluoro-immuno-magnetic separation technique (FIMS) in raw water taken from four purification plants and their water supplies in the department of Norte de Santander., Materials and Methods: The viruses were captured and separated from the water samples using magnetic microparticles functionalized with monoclonal anti-Hepatitis A and anti-Rotavirus antibodies. Confocal microscopy was used to monitor the viral concentration process and transmission electron microscopy for the morphological visualization of the separated viruses. The reverse transcriptase-coupled polymerase chain reaction (RT-PCR) was applied to confirm the presence of pathogens., Results: The two enteric viruses were identified in the majority of the analyzed water samples including water supply sources., Conclusion: We determined that the FIMS technique together with RT-PCR is highly effective for the detection of viral pathogens in complex matrices such as raw water.

The Receptor-Binding Domain (RBD) of the Spike (S) protein from Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has glycosylation sites which can limit the production of reliable antigens expressed in prokaryotic platforms, due to glycan-mediated evasion of the host immune response. However, protein regions without glycosylated residues capable of inducing neutralizing antibodies could be useful for antigen production in systems that do not carry the glycosylation machinery. To test this hypothesis, the potential antigens NG06 and NG19, located within the non-glycosylated S-RBD region, were selected and expressed in Escherichia coli , purified by FPLC and employed to determine their immunogenic potential through detection of antibodies in serum from immunized rabbits, mice, and COVID-19 patients. IgG antibodies from sera of COVID-19-recovered patients detected the recombinant antigens NG06 and NG19 (A 450 nm = 0.80 ± 0.33; 1.13 ± 0.33; and 0.11 ± 0.08 for and negatives controls, respectively). Also, the purified antigens were able to raise polyclonal antibodies in animal models evoking a strong immune response with neutralizing activity in mice model. This research highlights the usefulness of antigens based on the non-N-glycosylated region of RBD from SARS-CoV-2 for candidate vaccine development.

Dengue is a mosquito-borne disease that is of major importance in public health. Although it has been extensively studied at the molecular level, sequencing of the 5' and 3' ends of the untranslated regions (UTR) commonly requires specific approaches for completion and corroboration. The present study aimed to characterize the 5' and 3' ends of dengue virus types 1 to 4. The 5' and 3' ends of twenty-nine dengue virus isolates from acute infections were amplified through a modified protocol of the rapid amplification cDNA ends approach. For the 5' end cDNA synthesis, specific anti-sense primers for each serotype were used, followed by polyadenylation of the cDNA using a terminal transferase and subsequent PCR amplification with oligo(dT) and internal specific reverse primer. At the 3' end of the positive-sense viral RNA, an adenine tail was directly synthetized using an Escherichia coli poly(A) polymerase, allowing subsequent hybridization of the oligo(dT) during cDNA synthesis. The incorporation of the poly(A) tail at the 5' and 3' ends of the dengue virus cDNA and RNA, respectively, allowed for successful primer hybridization, PCR amplification and direct sequencing. This approach can be used for completing dengue virus genomes obtained through direct and next-generation sequencing methods.

A Zika virus (ZIKV) strain was isolated from an acute febrile patient during the Zika epidemics in Colombia. The strain was intraperitoneally inoculated into BALB/c mice, and 7 days postinoculation, neurological manifestations and ZIKV infection in the brain were demonstrated. The reported genome sequence is highly related to strains circulating in the Americas., (Copyright © 2019 Laiton-Donato et al.)

Background: Colombia was the second most affected country during the American Zika virus (ZIKV) epidemic, with over 109,000 reported cases. Despite the scale of the outbreak, limited genomic sequence data were available from Colombia. We sought to sequence additional samples and use genomic epidemiology to describe ZIKV dynamics in Colombia., Methods: We sequenced ZIKV genomes directly from clinical diagnostic specimens and infected Aedes aegypti samples selected to cover the temporal and geographic breadth of the Colombian outbreak. We performed phylogeographic analysis of these genomes, along with other publicly-available ZIKV genomes from the Americas, to estimate the frequency and timing of ZIKV introductions to Colombia., Results: We attempted PCR amplification on 184 samples; 19 samples amplified sufficiently to perform sequencing. Of these, 8 samples yielded sequences with at least 50% coverage. Our phylogeographic reconstruction indicates two separate introductions of ZIKV to Colombia, one of which was previously unrecognized. We find that ZIKV was first introduced to Colombia in February 2015 (95%CI: Jan 2015 - Apr 2015), corresponding to 5 to 8 months of cryptic ZIKV transmission prior to confirmation in September 2015. Despite the presence of multiple introductions, we find that the majority of Colombian ZIKV diversity descends from a single introduction. We find evidence for movement of ZIKV from Colombia into bordering countries, including Peru, Ecuador, Panama, and Venezuela., Conclusions: Similarly to genomic epidemiological studies of ZIKV dynamics in other countries, we find that ZIKV circulated cryptically in Colombia. More accurately dating when ZIKV was circulating refines our definition of the population at risk. Additionally, our finding that the majority of ZIKV transmission within Colombia was attributable to transmission between individuals, rather than repeated travel-related importations, indicates that improved detection and control might have succeeded in limiting the scale of the outbreak within Colombia.

We present Specific Reaction Parameter Multigrid POTFIT (SRP-MGPF), an automated methodology for the generation of global potential energy surfaces (PES), molecular properties surfaces, e.g., dipole, polarizabilities, etc. using a single random geometry as input. The SRP-MGPF workflow integrates: (i) a fully automated procedure for the global topographical characterization of a (intermolecular) PES based on the Transition State Search Using Chemical Dynamical Simulations (TSSCDS) family of methods;i (ii) the global optimization of the parameters of a semiempirical Hamiltonian in order to reproduce a given level of electronic structure theory; and (iii) a tensor decomposition algorithm which turns the resulting SRP-PES into sum of products (Tucker) form with the Multigrid POTFIT algorithm. The latter is necessary for quantum dynamical studies within the Multiconfiguration Time-Dependent Hartree (MCTDH) quantum dynamics method. To demonstrate our approach, we have applied our methodology to the cis-trans isomerization reaction in HONO in full dimensionality (6D). The resulting SRP-PES has been validated through the computation of classical on-the-fly dynamical calculations as well as calculations of the lowest vibrational eigenstates of HONO as well as high-energy wavepacket propagations.

Chikungunya virus (CHIKV) is considered a public health problem due to its rapid spread and high morbidity. This study aimed to determine the genetic diversity and phylogenetic relationships of CHIKVs in Colombia. A descriptive and retrospective study was carried out using sera of patients infected with Chikungunya during the outbreak in Colombia. The whole genomes of CHIKV (n = 16) were sequenced with an Illumina Hi-seq 2500 and were assembled using the Iterative Virus Assembler software. A Bayesian inference phylogenetic analysis was carried out with 157 strains of worldwide origin. The Colombian CHIKV sequences were grouped in the Asian genotype; however, three independent phylogenetic subclades were observed, probably the result of three separate introductions from Panama, Nicaragua, and St. Barts. Each subclade showed several different non-synonymous mutations (nsP2-A153V; nsp2-Y543H; nsp2-G720A; nsP3-L458P; Capside R78Q), that may have functional consequences for CHIKV biology and pathogenesis. These same mutations may affect the efficacy of potential CHIKV vaccines.

Dengue is hyperendemic in Colombia, where a cyclic behavior of serotype replacement leading to periodic epidemics has been observed for decades. This level of endemicity favors accumulation of dengue virus genetic diversity and could be linked to disease outcome. To assess the genetic diversity of dengue virus type 2 in Colombia, we sequenced the envelope gene of 24 virus isolates from acute cases of dengue or severe dengue fever during the period 2013-2016. The phylogenetic analysis revealed the circulation of the Asian-American genotype of dengue virus type 2 in Colombia during that period, the intra-genotype variability leading to divergence in two recently circulating lineages with differential geographic distribution, as well as the presence of nonsynonymous substitutions accompanying their emergence and diversification.

Introduction: Despite the availability of an effective vaccine and treatment to reduce the viral load and progressive hepatocellular injury, approximately 240 million people worldwide are chronically infected with the hepatitis B virus (HBV). In Colombia, the circulation of different viral genotypes has been confirmed. Mutations in the genome have been associated to antiviral therapy resistance, viral escape to neutralizing antibodies, occult infection and progression to hepatocellular carcinoma. Objective: To identify the genotypes and the presence of mutations in the coding region of the surface (S) antigen and the reverse transcriptase (RT) domain of the polymerase of HBV obtained from serum samples for hepatitis B diagnosis received by the Instituto Nacional de Salud during the period 2002-2014. Materials and methods: A total of 495 serum samples with previous HBsAg reactive result were used for molecular detection. A fragment of 1,591 nucleotides was sequenced, and the corresponding phylogenetic analysis was performed. Results: We detected the viral genome of HBV in 66 samples and 28 were successfully sequenced. The phylogenetic analysis allowed the identification of subgenotypes F3 and A2. The L180M and M204V resistance mutations were simultaneously identified in one sample, while the I169L resistance mutation was identified in another one. A single escape mutation, P120Q, was identified in one more. Two samples showed a deletion of 105 nucleotides in the preS1-preS2 region. Conclusions: The circulation of genotypes/subgenotypes F3 and A2 of HBV in Colombia was corroborated, as well as the presence of some resistance and escape mutations. The present study constitutes a contribution to the molecular epidemiology of HBV in Colombia.

The quantum photodynamics of a simple diatomic molecule with a permanent dipole immersed within an optical cavity containing a quantized radiation field is studied in detail. The chosen molecule under study, lithium fluoride (LiF), is characterized by the presence of an avoided crossing between the two lowest 1 Σ potential energy curves (covalent-ionic diabatic crossing). Without field, after prompt excitation from the ground state 1 1 Σ, the excited nuclear wave packet moves back and forth in the upper 2 1 Σ state, but in the proximity of the avoided crossing, the nonadiabatic coupling transfers part of the nuclear wave packet to the lower 1 1 Σ state, which eventually leads to dissociation. The quantized field of a cavity also induces an additional light crossing in the modified dressed potential energy curves with similar transfer properties. To understand the entangled photonic-nuclear dynamics, we solve the time-dependent Schrödinger equation by using the multiconfigurational time-dependent Hartree method (MCTDH). The single mode quantized field of the cavity is represented in the coordinate space instead of in the Fock space, which allows us to deal with the field as an additional vibrational mode within the MCTDH procedure on equal footing. We prepare the cavity with different quantum states of light, namely, Fock states, coherent states, and squeezed coherent states. Our results reveal pure quantum light effects on the molecular photodynamics and the dissociation yields of LiF, which are quite different from the light-undressed case and which cannot be described in general by a semiclassical approach using classical electromagnetic fields.

Introduction: Since drinking water can be a vehicle for the transmission of pathogens, the detection of enteric viruses in these water samples is essential to establish the appropriate measures to control and prevent associated diseases. , Objective: To analyze the results obtained for enteric viruses in water samples for human consumption received at the Colombian Instituto Nacional de Salud and establish their association with the data on water quality in Colombian municipalities. , Materials and Methods: We conducted a descriptive-retrospective analysis of the results obtained in the detection of rotavirus, enterovirus, hepatitis A virus and adenovirus in water samples received for complementary studies of enteric hepatitis, acute diarrheal disease and foodborne diseases. Data were correlated with the results of water quality surveillance determined by the national human consumption water quality index (IRCA). , Results: Of the 288 samples processed from 102 Colombian municipalities, 50.7% were positive for viruses: 26.73% for hepatitis A virus, 20.48% for enterovirus and rotavirus and 18.05% for adenovirus. Viruses were detected in 48.26% of non-treated water samples and in 45.83% of treated water samples. The IRCA index showed no correlation with the presence of viruses. , Conclusions: The presence of viruses in water represents a public health risk and, therefore, the prevention of virus transmission through water requires appropriate policies to reinforce water supply systems and improve epidemiological surveillance.

Introduction: Hepatitis A virus (HAV) is an important pathogen, typically transmitted via the faecal-oral route. The epidemiology of the infection is directly related to drinking water access and adequate disposal of sewage water. , Objective: To determine the presence and identify the genotype of HAV in environmental samples from eight municipalities and two villages in Antioquia, northwestern Colombia. , Materials and Methods: Three serial samplings were done between December, 2012, and April, 2014. Water samples were obtained from drinking water plants prior to treatment, as well as from the main reserve of wastewater in each municipality included in the study. Viral concentrations for the two types of sample sources were determined by filtration/tangential ultrafiltration and polyethyleneglycol plus flocculation with skimmed milk, respectively. Total ARN was subsequently obtained from each sample and the VP3-VP1 region amplified for detection of the viral genome. The genotype was determined by amplification of the VP1-2B region. , Results: The HAV genome was detected in samples from drinking water plants at Puerto Berrío, Frontino and Nutibara, and in wastewater samples from the municipalities of Arboletes, Zaragoza and Venecia. HAV subgenotype IA was identified using phylogenetic analysis. , Conclusion: In this study, HAV was identified in 6.6% of the samples from drinking water plants and 13.3% of wastewater samples. This is the first report of HAV subgenotype IA circulating in environmental samples from Antioquia.

Introduction: Hepatitis E virus has emerged as a public health problem, particularly in developing countries. The four genotypes identified in mammals include the G3 found in indigenous hepatitis in countries and regions with high porcine population, and the G1, associated with maternal deaths. , Objective: To determine coinfection by hepatitis E virus and the circulating genotypes in Colombia in 1,097 samples using serological markers for hepatitis A, B and C. , Materials and Methods: Serum samples of 1,097 patients from different regions of Colombia stored at the Laboratorio de Virología of the Instituto Nacional de Salud were selected to detect IgG and IgM anti-hepatitis E virus antibodies. The viral genomes of positive samples were amplified by RT-PCR, and the products were sequenced and phylogenetically analyzed by comparing ORF2 sequences deposited in the GenBank. , Results: IgG anti-hepatitis E virus antibodies were found in 278 samples, IgM in 62, and both markers in 64. Hepatitis E virus and hepatitis A virus coinfection determined by IgG anti-hepatitis E virus was 33.6% and 16.1% by IgM; hepatitis E virus and hepatitis B virus coinfection was 23.4% and 8.1%, and hepatitis E virus and hepatitis C virus coinfection was 35.4% and 5.83%, respectively. Among the 52 positive samples by PCR nine were sequenced and grouped within genotype 3A of the American porcine strain. , Conclusions: The highest seropositivity was observed for hepatitis A and E. The incidence of hepatitis E virus coinfection with other hepatotropic viruses indicated that this pathogen is more frequent than expected. The circulation of genotype 3A implies that this disease may occur in outbreaks and as zoonosis in Colombia.

Introduction: Hepatitis E virus (HEV) is an emergent virus of global importance; it is the etiological agent of sporadic cases and outbreaks of hepatitis. The epidemiology of this infection in Colombia is unknown., Objective: To determine the seropositivity for hepatitis E virus in Colombia in cases with clinical diagnosis of viral hepatitis., Materials and Methods: Serum samples from patients that were sent to the Instituto Nacional de Salud during the period 2005-2010 (group 1) and samples sent to the Laboratorio Departamental de Salud Pública de Antioquia during the 2008-2009 period were included in this study (group 2). Serum samples were analyzed by immunoassay with commercial kits., Results: From the 344 analyzed samples, 8.7% were positive for anti-HEV; the frequency of anti-HEV IgM was 1.74% (6/344) and the frequency of anti-HEV IgG was 7.5% (26/344). A difference in frequency of anti-HEV between group 1 (6.3%) and group 2 (1.3%) was observed. The cases were identified in nine departments of Colombia., Conclusions: This is the first study of hepatitis E virus infection in patients with diagnosis of hepatitis in Colombia. The frequency of anti-HEV described in this population of patients in Colombia is similar to that described in other Latin American countries like Brazil, Perú and Uruguay. Considering the results of this study, it could be necessary to include hepatitis E virus infection serological markers in the differential diagnosis of viral hepatitis in Colombia.

The study of excited triplet states of a molecular system is a difficult task because accessing them involves forbidden transitions from the singlet ground state. Nevertheless, absorption spectra of many molecules present, at low energies, the weak fingerprint of these triplet states. At higher energies this information is usually masked by the intense signal of the singlet states. Here we show, for the specific case of the sulphur dioxide molecule, that the combined use of polarized light and molecular alignment can enhance the triplet part of the spectrum, even making it the only absorption process.

Introduction. Vascular endothelial growth factor (VEGF), an angiogenic factor secreted by type II pneumocytes, could play a role in congenital diaphragmatic hernia (CDH) pathogenesis. Animal studies suggest that VEGF accelerates lung growth. Aim. To quantify VEGF on fetal lungs in a nitrofen rat model for CDH and to analyze the effect of tracheal occlusion (TO) in VEGF in fetal lung rats after nitrofen and in control rats not exposed to nitrofen. Methods. Pregnant rats received nitrofen on day 9.5 of gestation. Fetuses were divided into 2 groups: those that underwent TO on day 20 and those that did not. On day 21, fetuses were delivered, and the lungs were dissected for subsequent VEGF quantification. Results. CDH was detected in 43% of the fetuses that received nitrofen. Fetuses with CDH showed significantly reduced lung weight/fetal weight ratio and lower VEGF levels than the remainder. A higher VEGF value was observed after TO. Conclusions. VEGF protein was significantly lower in fetuses with CDH. TO induced a significant increase in VEGF compared to the fetuses that did not undergo TO. Although not statistically significant, we observed higher VEGF levels in fetuses with CDH and TO compared to fetuses with CDH and no further intervention.

Introduction: Enteric viruses have been implicated in acute diarrheal disease, food-borne disease, hepatitis A and meningitis outbreaks, in which water was the vehicle of transmission., Objective: A concentration method was standardized for the detection of enteric viruses in drinking water., Materials and Methods: Twenty liters of water were concentrated to 6 ml by filtration and tangential ultrafiltration. Viral solutions of 20 L each were prepared at 1, 10, 50 and 100 TCID50 of Sabin poliovirus type 1 as positive controls. Viral particles were recovered by tissue culture and detected by conventional polymerase chain reaction (PCR), according to the international standards recommended by the Enterovirus Laboratory at the Centers for Disease Control and Prevention, Atlanta, GA., Results: All positive controls showed cytopathic effect on L20B and RD cells and were amplified by conventional PCR directly from samples. Negative controls did not show any amplification or viral cytopathic effect., Conclusions: Tangential ultrafiltration for concentrating viruses proved to be a fast, efficient recovery and reproducible. It has the advantage of allowing the detection (at the 1 TCID50 level) and identification of viruses by RT-PCR and the demonstration of viral infectivity by tissue culture.

Surface-enhanced Raman scattering (SERS) of hydroxybenzoic acids has been studied on silver sols in H(2)O and D(2)O solutions. The adsorption behavior of 4-hydroxybenzoic acid (4HBA) is different from that of salicylic (2HBA) and 3-hydroxybenzoic (3HBA) acids. It was concluded that 4HBA is adsorbed on silver nanoparticles (Ag(n)) as either oxidobenzoate (A(2-)) or hydroxybenzoate (A(-)), depending on the pH of the solution, given rise to a flat orientation. Both 2HBA and 3HBA acids are always adsorbed as hydroxybenzoates anions (A(-)) at pH >or=5 and link to the metal through the carboxylate group (Ag(n)--A(-)), standing more or less perpendicular to the metal surface. In the case of these monoanions, the selective enhancement of the bands is due mainly to a resonant electron or charge transfer process (ET or CT) from the metallic nanoparticles to the adsorbates, yielding the transient formation of the respective radical dianions (Ag(+)(n)--A(2-)). It is found that the enhanced bands, and especially the mode 8a;nu(ring), are related to the difference between the equilibrium structures of the adsorbate in its ground (A(-)) and CT-excited (A(2-)) states. In the SERS spectrum of 4HBA dianion, the contribution of CT mechanism is not observed.

The photochemical behavior of the protonated simplest nitrosamine [NH2NO-H](+) has been addressed by means of the CASPT2//CASSCF methodology in conjunction with the ANO-L basis sets. The relative stability of the different tautomers, namely, (1) NH2NOH(+), (2) NH3NO(+), and (3) NH2NHO(+), has been considered, and the corresponding tautomerization transition states have been characterized. With respect to the most chemically relevant species, it has been found that NH2NOH(+) corresponds to a bound structure, while NH3NO(+) corresponds to an adduct between NH3 and NO(+) at both CASSCF and CASPT2 levels of theory. Vertical transition calculations and linear interpolations on the homolytic dissociation of NH3NO(+) in combination with previous results on neutral nitrosamine [J. Chem. Phys. 2006, 125, 164311] and neutral N,N-dimethylnitrosamine [J. Org. Chem. 2007, 72, 4741] indicate that, in acidic diluted solutions, the protonation of nitrosamine takes place on the excited surface. The N-N dissociation channels have been studied both in ground and first excited singlet state. An S1/S0 conical intersection is found to be responsible for the photostability of NH2NOH(+). On the contrary, NH3NO(+) is photochemically unstable as its first excited state is purely dissociative. The latter species is characterized by a twofold reactivity: the formation of nitrosyl cation (NO(+)) in the ground state and the photorelease of physiologically relevant nitric oxide radical (NO) in its first excited state.

The photochemistry of N-nitrosodimethylamine after excitation to the S(1) and S(2) states has been studied with the complete active space self-consistent field method (CASSCF) and the second-order multiconfigurational perturbation theory (CASPT2). The calculated vertical transitions agree with the experiment: the S(0) --> S(1) transition occurs at 3.29 eV (f = 0.003 au), the S(0) --> S(2) transition at 5.30 eV (f = 0.17 au) and the first excited triplet state is computed at 2.48 eV. Solvent effects have been reproduced by means of PCM calculations. It is shown that excitation to S(1) and S(2) yields the same photoproducts: (CH(3))(2)N (1(2)B(1)) and NO (X(2)Pi). However, while on S1 the process is adiabatic, the process on S(2) implies an ultrafast decay through a planar S(2)/S(1) conical intersection. Our calculations are consistent with the reversibility of the N-N dissociation after irradiation at 363.5 nm and the observed dimethylamine radical reactions when irradiated at 248 nm, namely, H extrusion, a one-step process (41.3 kcal/mol), and methyl radical extrusion, a two-step process (44.0 kcal/mol and 31.5 kcal/mol). Finally, two more aspects are considered: (i) the topology of the T(1) surface where two minima have been found to correlate with the phosphorescence emission band and (ii) the influence of tautomerizations which is shown to be neglectable.

Ultrafast decay processes detected after absorption of UV radiation in gas-phase pyrimidine nucleobases uracil, thymine, and cytosine are ascribed to the barrierless character of the pathway along the low-lying 1(pipi*) hypersurface connecting the Franck-Condon region with an out-of-plane distorted ethene-like conical intersection with the ground state. Longer lifetime decays and low quantum yield emission are on the other hand related to the presence of a 1(pipi*) state planar minimum on the S1 surface and the barriers to access other conical intersections. A unified model for the three systems is established on the basis of accurate multiconfigurational CASPT2 calculations, whereas the effect of the different levels of theory on the results is carefully analyzed.

The dissociation reaction of nitrosomethane into methyl and nitric oxide and the tautomerization reactions to formaldehyde oxime, nitrone, and methoxy nitrene have been studied with the second-order multiconfigurational perturbation theory (CASPT2) by the computation of numerical energy gradients. The prevailing reactions in both the ground and the excited states are dissociations. The structures of the ground and excited states are compared with the corresponding complete active space SCF (CAS-SCF) geometries. It is found that changes in the individual bond lengths are rather large (0.01-0.02 A), while the character and energetics of the CASPT2 optimizations remain similar to the CAS-SCF values.