Bacteria-Derived Cellulose Membranes Modified with Graphene Oxide-Silver Nanoparticles for Accelerating Wound Healing.

This study reports on the modification of bacterial cellulose (BC) membranes produced by static fermentation of Komagataeibacter xylinus bacterial strains with graphene oxide-silver nanoparticles (GO-Ag) to yield skin wound dressings with improved antibacterial properties. The GO-Ag sheets were synthesized through chemical reduction with sodium citrate and were utilized to functionalize the BC membranes (BC/GO-Ag). The BC/GO-Ag composites were characterized to determine their surface charge, morphology, exudate absorption, antimicrobial activity, and cytotoxicity by using fibroblast cells. The antimicrobial activity of the wound dressings was assessed against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The results indicate that the BC/GO-Ag dressings can inhibit ∼70% of E. coli cells. Our findings also revealed that the porous BC/GO-Ag antimicrobial dressings can efficiently retain 94% of exudate absorption after exposure to simulated body fluid (SBF) for 24 h. These results suggest that the dressings could absorb excess exudate from the wound during clinical application, maintaining adequate moisture, and promoting the proliferation of epithelial cells. The BC/GO-Ag hybrid materials exhibited excellent mechanical flexibility and low cytotoxicity to fibroblast cells, making excellent wound dressings able to control bacterial infectious processes and promote the fast healing of dermal lesions.

Nanoparticles and plants: A focus on analytical characterization techniques.

Nanotechnology has brought about significant progress through the use of goods based on nanomaterials. However, concerns remain about the accumulation of these materials in the environment and their potential toxicity to living organisms. Plants have the ability to take in nanomaterials (NMs), which can cause changes in their physiology and morphology. On the other hand, nanoparticles (NPs) have been used to increase plant development and control pests in agriculture by including them into agrochemicals. The challenges of the interaction, internalization, and accumulation of NMs within plant tissues are enormous, mainly because of the various characteristics of NMs and the absence of reliable analytical tools. As our knowledge of the interactions between NMs and plant cells expands, we are able to create novel NMs that are tailored, targeted, and designed to be safe, thus minimizing the environmental consequences of nanomaterials. This review provides a thorough examination and comparison of the main microscopy techniques, spectroscopic methods, and far-field super-resolution methodologies used to examine nanomaterials within the cell walls of plants.

Hepatic endotheliitis in Golden Syrian hamsters (Mesocricetus auratus) experimentally infected with SARS-CoV-2.

Hepatic injuries in COVID-19 are not yet fully understood and indirect pathways (without viral replication in the liver) have been associated with the activation of vascular mechanisms of liver injury in humans infected with SARS-CoV-2. Golden Syrian hamsters are an effective model for experimental reproduction of moderate and self-limiting lung disease during SARS-CoV-2 infection. As observed in humans, this experimental model reproduces lesions of bronchointerstitial pneumonia and pulmonary vascular lesions, including endotheliitis (attachment of lymphoid cells to the luminal surface of endothelium). Extrapulmonary vascular lesions are well documented in COVID-19, but such extrapulmonary vascular lesions have not yet been described in the Golden Syrian hamster model of SARS-CoV-2 infection. The study aimed to evaluate microscopic liver lesions in Golden Syrian hamsters experimentally infected with SARS-CoV-2. In total, 38 conventional Golden Syrian hamsters, divided into infected group (n=24) and mock-infected group (n=14), were euthanized at 2-, 3-, 4-, 5-, 7-, 14-, and 15-days post infection with SARS-CoV-2. Liver fragments were evaluated by histopathology and immunohistochemical detection of SARS-CoV-2 Spike S2 antigens. The frequencies of portal vein endotheliitis, lobular activity, hepatocellular degeneration, and lobular vascular changes were higher among SARS-CoV-2-infected animals. Spike S2 antigen was not detected in liver. The main results indicate that SARS-CoV-2 infection exacerbated vascular and inflammatory lesions in the liver of hamsters with pre-existing hepatitis of unknown origin. A potential application of this animal model in studies of the pathogenesis and evolution of liver lesions associated with SARS-CoV-2 infection still needs further evaluation.

Antibodies against Leptospira spp. in Free-living and Captive Broad-snouted Caiman (Caiman latirostris) and Free-living Yacare Caiman (Caiman yacare) in Brazil.

We evaluated antibodies against Leptospira spp. in both free-living and captive Caiman latirostris from Atlantic Forest, and free-living Caiman yacare from Pantanal, Brazil, by using a microscopic agglutination test. Overall seropositivity was 17%, with rates of 36% in captive C. latirostris (n=4/11) and 18% in free-living C. yacare (n=4/22).

Hepatic endotheliitis in Golden Syrian hamsters (Mesocricetus auratus) experimentally infected with SARS-CoV-2

ABSTRACT Hepatic injuries in COVID-19 are not yet fully understood and indirect pathways (without viral replication in the liver) have been associated with the activation of vascular mechanisms of liver injury in humans infected with SARS-CoV-2. Golden Syrian hamsters are an effective model for experimental reproduction of moderate and self-limiting lung disease during SARS-CoV-2 infection. As observed in humans, this experimental model reproduces lesions of bronchointerstitial pneumonia and pulmonary vascular lesions, including endotheliitis (attachment of lymphoid cells to the luminal surface of endothelium). Extrapulmonary vascular lesions are well documented in COVID-19, but such extrapulmonary vascular lesions have not yet been described in the Golden Syrian hamster model of SARS-CoV-2 infection. The study aimed to evaluate microscopic liver lesions in Golden Syrian hamsters experimentally infected with SARS-CoV-2. In total, 38 conventional Golden Syrian hamsters, divided into infected group (n=24) and mock-infected group (n=14), were euthanized at 2-, 3-, 4-, 5-, 7-, 14-, and 15-days post infection with SARS-CoV-2. Liver fragments were evaluated by histopathology and immunohistochemical detection of SARS-CoV-2 Spike S2 antigens. The frequencies of portal vein endotheliitis, lobular activity, hepatocellular degeneration, and lobular vascular changes were higher among SARS-CoV-2-infected animals. Spike S2 antigen was not detected in liver. The main results indicate that SARS-CoV-2 infection exacerbated vascular and inflammatory lesions in the liver of hamsters with pre-existing hepatitis of unknown origin. A potential application of this animal model in studies of the pathogenesis and evolution of liver lesions associated with SARS-CoV-2 infection still needs further evaluation.

Effects of chemical aging on carbonaceous materials: Stability of water-dispersible colloids and their influence on the aggregation of natural-soil colloid.

Although hydrochar and biochar have been used as soil conditioners, there is not a clear understanding of how their properties changes due to aging impacts their colloidal particles behavior on the soil system. From this premise, we produced hydrochar and biochar from the same feedstock (cashew bagasse) and aged with different chemical methods: (i) using hydrogen peroxide, (ii) a mixture of nitric and sulfuric acids, and (iii) hot water. It was analyzed the effects of aging on the stability of the carbonaceous materials (CMs) colloids in aqueous medium with different ionic strength (single systems), as well as the stability of the natural-soil colloid when interacting with biochar and hydrochar colloids (binary systems). A chemical composition (C, H, N, and O content) change in CMs due to the chemically induced aging was observed along with minor structural modifications. Chemical aging could increase the amount of oxygen functional groups for both biochar and hydrochar, though in a different level depending on the methodology applied. In this sense, hydrochar was more susceptive to chemical oxidation than biochar. The effectiveness of chemical aging treatments for biochar increased in the order of water < acid < hydrogen peroxide, whereas for hydrochar the order was water < hydrogen peroxide < acid. While the increase in surface oxidation improved the biochar colloidal stability in water medium at different ionic strengths (single systems), the stability and critical coagulation concentration (CCC) slightly changed for hydrochar. Natural-soil clay (NSC) interactions with oxidized carbonaceous material colloids (binary systems) enhanced NSC stability, which is less likely to aggregate. Therefore, the aging of carbonaceous materials modifies the interaction and dynamics of soil small particles, requiring far more attention to the environmental risks due to their application over time.

Impact of an autophagy-inducing peptide on immunogenicity and protection efficacy of an adenovirus-vectored SARS-CoV-2 vaccine.

Because of continual generation of new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it is critical to design the next generation of vaccines to combat the threat posed by SARS-CoV-2 variants. We developed human adenovirus (HAd) vector-based vaccines (HAd-Spike/C5 and HAd-Spike) that express the whole Spike (S) protein of SARS-CoV-2 with or without autophagy-inducing peptide C5 (AIP-C5), respectively. Mice or golden Syrian hamsters immunized intranasally (i.n.) with HAd-Spike/C5 induced similar levels of S-specific humoral immune responses and significantly higher levels of S-specific cell-mediated immune (CMI) responses compared with HAd-Spike vaccinated groups. These results indicated that inclusion of AIP-C5 induced enhanced S-specific CMI responses and similar levels of virus-neutralizing titers against SARS-CoV-2 variants. To investigate the protection efficacy, golden Syrian hamsters immunized i.n. either with HAd-Spike/C5 or HAd-Spike were challenged with SARS-CoV-2. The lungs and nasal turbinates were collected 3, 5, 7, and 14 days post challenge. Significant reductions in morbidity, virus titers, and lung histopathological scores were observed in immunized groups compared with the mock- or empty vector-inoculated groups. Overall, slightly better protection was seen in the HAd-Spike/C5 group compared with the HAd-Spike group.

Substrate-Induced Changes on the Optical Properties of Single-Layer WS2.

Among the most studied semiconducting transition metal dichalcogenides (TMDCs), WS2 showed several advantages in comparison to their counterparts, such as a higher quantum yield, which is an important feature for quantum emission and lasing purposes. We studied transferred monolayers of WS2 on a drilled Si3N4 substrate in order to have insights about on how such heterostructure behaves from the Raman and photoluminescence (PL) measurements point of view. Our experimental findings showed that the Si3N4 substrate influences the optical properties of single-layer WS2. Beyond that, seeking to shed light on the causes of the PL quenching observed experimentally, we developed density functional theory (DFT) based calculations to study the thermodynamic stability of the heterojunction through quantum molecular dynamics (QMD) simulations as well as the electronic alignment of the energy levels in both materials. Our analysis showed that along with strain, a charge transfer mechanism plays an important role for the PL decrease.

Assessing the Fate of Superparamagnetic Iron Oxide Nanoparticles Carrying Usnic Acid as Chemical Cargo on the Soil Microbial Community.

In the present study we evaluate the effect of superparamagnetic iron oxide nanoparticles (SPIONs) carrying usnic acid (UA) as chemical cargo on the soil microbial community in a dystrophic red latosol (oxysol). Herein, 500 ppm UA or SPIONs-framework carrying UA were diluted in sterile ultrapure deionized water and applied by hand sprayer on the top of the soil. The experiment was conducted in a growth chamber at 25 °C, with a relative humidity of 80% and a 16 h/8 h light-dark cycle (600 lx light intensity) for 30 days. Sterile ultrapure deionized water was used as the negative control; uncapped and oleic acid (OA) capped SPIONs were also tested to assess their potential effects. Magnetic nanostructures were synthesized by a coprecipitation method and characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), zeta potential, hydrodynamic diameter, magnetic measurements, and release kinetics of chemical cargo. Uncapped and OA-capped SPIONs did not significantly affect soil microbial community. Our results showed an impairment in the soil microbial community exposed to free UA, leading to a general decrease in negative effects on soil-based parameters when bioactive was loaded into the nanoscale magnetic carrier. Besides, compared to control, the free UA caused a significant decrease in microbial biomass C (39%), on the activity of acid protease (59%), and acid phosphatase (23%) enzymes, respectively. Free UA also reduced eukaryotic 18S rRNA gene abundance, suggesting a major impact on fungi. Our findings indicate that SPIONs as bioherbicide nanocarriers can reduce the negative impacts on soil. Therefore, nanoenabled biocides may improve agricultural productivity, which is important for food security due to the need of increasing food production.

Acute toxicity of titanium dioxide microparticles in Artemia sp. nauplii instar I and II.

In this study, the toxicity effects of titanium dioxide (MTiO2 ) microparticles on Artemia sp. nauplii instar I and II between 24 and 48 h was evaluated. The MTiO2 were characterized using different microscopy techniques. MTiO2 rutile was used in toxicity tests at concentration of 12.5, 25, 50, and 100 ppm. No toxicity was observed in Artemia sp. nauplii instar I at the time of 24 and 48 h. However, Artemia sp. nauplii instar II toxicity was observed within 48 h of exposure. MTiO2 at concentrations of 25, 50 and 100 ppm was lethal for Artemia sp. with a significant difference (p ≤ .05) in relation to the control artificial sea water with LC50 value at 50 ppm. Analysis of optical and scanning electron microscopy revealed tissue damage and morphological changes in Artemia sp. nauplii instar II. By using confocal laser scanning microscopy, cell damage was observed due to the toxicity of MTiO2 at a concentration of 20, 50, and 100 ppm. The high mortality rate is related to the filtration of MTiO2 by Artemia sp. nauplii instar II due to the complete development of the digestive tract.

Chemical Evaluation, Phytotoxic Potential, and In Silico Study of Essential Oils from Leaves of Guatteria schomburgkiana Mart. and Xylopia frutescens Aubl. (Annonaceae) from the Brazilian Amazon.

The essential oils (EOs) of Guatteria schomburgkiana (Gsch) and Xylopia frutescens (Xfru) (Annonaceae) were obtained by hydrodistillation, and their chemical composition was evaluated by gas chromatography-mass spectrometry (GC/MS). Herbicide activity was measured by analyzing the seed germination percentage and root and hypocotyl elongation of two invasive species: Mimosa pudica and Senna obtusifolia. The highest yield was obtained for the EO of Xfru (1.06%). The chemical composition of Gsch was characterized by the presence of the oxygenated sesquiterpenes spathulenol (22.40%) and caryophyllene oxide (14.70%). Regarding the EO of Xfru, the hydrocarbon monoterpenes α-pinene (35.73%) and ß-pinene (18.90%) were the components identified with the highest concentrations. The germination of seeds of S. obtusifolia (13.33 ± 5.77%) showed higher resistance than that of seeds of M. pudica (86.67 ± 5.77%). S. obtusifolia was also more sensitive to the EO of Xfru in terms of radicle (55.22 ± 2.72%) and hypocotyl (71.12 ± 3.80%) elongation, while M. pudica showed greater sensitivity to the EO of Gsch. To screen the herbicidal activity, the molecular docking study of the major and potent compounds was performed against 4-hydroxyphenylpyruvate dioxygenase (HPPD) protein. Results showed good binding affinities and attributed the strongest inhibitory activity to δ-cadinene for the target protein. This work contributes to the study of the herbicidal properties of the EOs of species of Annonaceae from the Amazon region.

Phytochemical Profile and Herbicidal (Phytotoxic), Antioxidants Potential of Essential Oils from Calycolpus goetheanus (Myrtaceae) Specimens, and in Silico Study.

The essential oil (EO) of Calycolpus goetheanus (Myrtaceae) specimens (A, B, and C) were obtained through hydrodistillation. The analysis of the chemical composition of the EOs was by gas chromatography coupled with mass spectrometry CG-MS, and gas chromatography coupled with a flame ionization detector CG-FID. The phytotoxic activity of those EOs was evaluated against two weed species from common pasture areas in the Amazon region: Mimosa pudica L. and Senna obtusifolia (L.) The antioxidant capacity of the EOs was determined by (DPPH•) and (ABTS•+). Using molecular docking, we evaluated the interaction mode of the major EO compounds with the molecular binding protein 4-hydroxyphenylpyruvate dioxygenase (HPPD). The EO of specimen A was characterized by ß-eudesmol (22.83%), (E)-caryophyllene (14.61%), and γ-eudesmol (13.87%), while compounds 1,8-cineole (8.64%), (E)-caryophyllene (5.86%), δ-cadinene (5.78%), and palustrol (4.97%) characterize the chemical profile of specimen B's EOs, and specimen C had α-cadinol (9.03%), δ-cadinene (8.01%), and (E)-caryophyllene (6.74%) as the majority. The phytotoxic potential of the EOs was observed in the receptor species M. pudica with percentages of inhibition of 30%, and 33.33% for specimens B and C, respectively. The EOs' antioxidant in DPPH• was 0.79 ± 0.08 and 0.83 ± 0.02 mM for specimens A and B, respectively. In the TEAC, was 0.07 ± 0.02 mM for specimen A and 0.12 ± 0.06 mM for specimen B. In the results of the in silico study, we observed that the van der Waals and hydrophobic interactions of the alkyl and pi-alkyl types were the main interactions responsible for the formation of the receptor-ligand complex.

In Silico Evaluation of the Antimicrobial Activity of Thymol-Major Compounds in the Essential Oil of Lippia thymoides Mart. & Schauer (Verbenaceae).

In this paper, we evaluated the drug-receptor interactions responsible for the antimicrobial activity of thymol, the major compound present in the essential oil (EO) of Lippia thymoides (L. thymoides) Mart. & Schauer (Verbenaceae). It was previously reported that this EO exhibits antimicrobial activity against Candida albicans (C. albicans), Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli). Therefore, we used molecular docking, molecular dynamics simulations, and free energy calculations to investigate the interaction of thymol with pharmacological receptors of interest to combat these pathogens. We found that thymol interacted favorably with the active sites of the microorganisms' molecular targets. MolDock Score results for systems formed with CYP51 (C. albicans), Dihydrofolate reductase (S. aureus), and Dihydropteroate synthase (E. coli) were -77.85, -67.53, and -60.88, respectively. Throughout the duration of the MD simulations, thymol continued interacting with the binding pocket of the molecular target of each microorganism. The van der Waals (ΔEvdW = -24.88, -26.44, -21.71 kcal/mol, respectively) and electrostatic interaction energies (ΔEele = -3.94, -11.07, -12.43 kcal/mol, respectively) and the nonpolar solvation energies (ΔGNP = -3.37, -3.25, -2.93 kcal/mol, respectively) were mainly responsible for the formation of complexes with CYP51 (C. albicans), Dihydrofolate reductase (S. aureus), and Dihydropteroate synthase (E. coli).

SARS-CoV-2 infection impacts carbon metabolism and depends on glutamine for replication in Syrian hamster astrocytes.

COVID-19 causes more than million deaths worldwide. Although much is understood about the immunopathogenesis of the lung disease, a lot remains to be known on the neurological impact of COVID-19. Here, we evaluated immunometabolic changes using astrocytes in vitro and dissected brain areas of SARS-CoV-2 infected Syrian hamsters. We show that SARS-CoV-2 alters proteins of carbon metabolism, glycolysis, and synaptic transmission, many of which are altered in neurological diseases. Real-time respirometry evidenced hyperactivation of glycolysis, further confirmed by metabolomics, with intense consumption of glucose, pyruvate, glutamine, and alpha ketoglutarate. Consistent with glutamine reduction, the blockade of glutaminolysis impaired viral replication and inflammatory response in vitro. SARS-CoV-2 was detected in vivo in hippocampus, cortex, and olfactory bulb of intranasally infected animals. Our data evidence an imbalance in important metabolic molecules and neurotransmitters in infected astrocytes. We suggest this may correlate with the neurological impairment observed during COVID-19, as memory loss, confusion, and cognitive impairment.

Anti-SARS-CoV-2 equine F (Ab')2 immunoglobulin as a possible therapy for COVID-19.

The new outbreak of coronavirus disease 2019 (COVID-19) has infected and caused the death of millions of people worldwide. Intensive efforts are underway around the world to establish effective treatments. Immunoglobulin from immunized animals or plasma from convalescent patients might constitute a specific treatment to guarantee the neutralization of the virus in the early stages of infection, especially in patients with risk factors and a high probability of progressing to severe disease. Worldwide, a few clinical trials using anti-SARS-CoV-2 immunoglobulins from horses immunized with the entire spike protein or fragments of it in the treatment of patients with COVID-19 are underway. Here, we describe the development of an anti-SARS-CoV-2 equine F(ab')2 immunoglobulin using a newly developed SARS-CoV-2 viral antigen that was purified and inactivated by radiation. Cell-based and preclinical assays showed that the F(ab')2 immunoglobulin successfully neutralizes the virus, is safe in animal models, and reduces the severity of the disease in a hamster model of SARS-CoV-2 infection and disease.

Profiles not metrics: the case of Brazilian universities.

Public universities, and science in general, in Brazil, are under attack from key persons of the government in interviews and articles published in non-scientific journals. Here we look at bibliography data from international science metric platforms (Scival® and Incites®) and official Brazilian agencies such as CAPES and CNPq to reach some conclusions based on scientific analysis. Brazilian Science has shown a steady improvement in quantity and quality over the last 20 years but has recently suffered (since 2015) under severe financial restrictions. An increase in international collaboration also increased citation impact, reaching almost five times the world average. While the medical and natural sciences show the highest impact and prominence, social sciences and the humanities also have spotlight areas with international excellence. Different research institutions and universities offer a variety of production profiles and impacts. This diagnosis shows the need for universities and research institutes in Brazil and funding agencies to undergo strategic planning for definition of mission/vision, goals to be reached, and areas for priority development. Continued support of public universities by the government is necessary for Brazilian autonomy in science and technology and its full integration in the world scientific community.

Silver nanoparticles (AgNPs) internalization and passage through the Lactuca sativa (Asteraceae) outer cell wall.

Silver nanoparticle (AgNPs) toxicity is related to nanoparticle interaction with the cell wall of microorganisms and plants. This interaction alters cell wall conformation with increased reactive oxygen species (ROS) in the cell. With the increase of ROS in the cell, the dissolution of zero silver (Ag0) to ionic silver (Ag+) occurs, which is a strong oxidant agent to the cellular wall. AgNP interaction was evaluated by transmission electron microscopy (TEM) on Lactuca sativa roots, and the mechanism of passage through the outer cell wall (OCW) was also proposed. The results suggest that Ag+ binds to the hydroxyls (OH) present in the cellulose structure, thus causing the breakdown of the hydrogen bonds. Changes in cell wall structure facilitate the passage of AgNPs, reaching the plasma membrane. According to the literature, silver nanoparticles with an average diameter of 15nm are transported across the membrane into the cells by caveolines. This work describes the interaction between AgNPs and the cell wall and proposes a transport model through the outer cell wall.

Sperm viability, serological, molecular, and modified seminal plasma agglutination tests in the diagnosis of Leptospira in the semen and serum of bovine bulls.

The present study investigated the serum microscopic agglutination test (MAT) among 203 bovine bulls with reproduction by natural means, without apparent signs of orchitis or inflammation of accessory reproductive glands. Simultaneously, the semen of all bulls was subjected to sperm viability analysis and PCR based on the 16S rRNA gene. PCR-positive results of semen samples were confirmed by sequencing. A modified seminal plasma agglutination (MSPA) test, replacing the blood serum of all bulls in the MAT with seminal plasma was performed as well. Eight (8/203 = 3.9%) semen samples from bulls were considered nonviable (necrospermia and azoospermia) without relation to the PCR diagnosis. No agglutinin titers were identified in MSPA test. A high frequency (132/203 = 65%) of leptospiral agglutinin titers was identified in the MAT, particularly for the Sejroe serogroup (Hardjo CTG, 100/203 = 49.3%; Wolffi 74/203 = 36.4%; Guaricura 72/203 = 35.5%; and Hardjoprajitno 56/203 = 27.6%). Three (3/203 = 1.5%) semen samples of bulls were positive in the PCR, but these results were not confirmed by sequencing. The high frequency of serovars from the Sejroe serogroup typically adapted to bovines indicates the need for measures for the prophylaxis/control of the pathogen on the sampled farms. Discrepancies among the MAT, sperm viability, and molecular detection of leptospires in semen highlight the need for a combination of methods to diagnose leptospirosis in bovine bulls. To our knowledge, modified seminal plasma agglutination is described for the first time here to investigate anti-Leptospira antibodies produced locally in the genital tract in the diagnosis of bovine leptospirosis among bulls that reproduce by natural means.

Chemical Composition of Volatile Compounds in Apis mellifera Propolis from the Northeast Region of Pará State, Brazil.

Propolis is a balsamic product obtained from vegetable resins by exotic Africanized bees Apis mellifera L., transported and processed by them, originating from the activity that explores and maintains these individuals. Because of its vegetable and natural origins, propolis is a complex mixture of different compound classes; among them are the volatile compounds present in the aroma. In this sense, in the present study we evaluated the volatile fraction of propolis present in the aroma obtained by distillation and simultaneous extraction, and its chemical composition was determined using coupled gas chromatography, mass spectrometry, and flame ionization detection. The majority of compounds were sesquiterpene and hydrocarbons, comprising 8.2-22.19% α-copaene and 6.2-21.7% ß-caryophyllene, with additional compounds identified in greater concentrations. Multivariate analysis showed that samples collected from one region may have different chemical compositions, which may be related to the location of the resin's production. This may be related to other bee products.

Origin of the Giant Enhanced Raman Scattering by Sulfur Chains Encapsulated inside Single-Wall Carbon Nanotubes.

In this work, we explain the origin and the mechanism responsible for the strong enhancement of the Raman signal of sulfur chains encapsulated by single-wall carbon nanotubes by running resonance Raman measurements in a wide range of excitation energies for two nanotube samples with different diameter distributions. The Raman signal associated with the vibrational modes of the sulfur chain is observed when it is confined by small-diameter metallic nanotubes. Moreover, a strong enhancement of the Raman signal is observed for excitation energies corresponding to the formation of excited nanotube-chain-hybrid electronic states. Our hypothesis was further tested by high pressure Raman measurements and confirmed by density functional theory calculations of the electronic density of states of hybrid systems formed by sulfur chains encapsulated by different types of single-wall carbon nanotubes.