New Developments of Laser Desorption Ionization Mass Spectrometry in Natural Products Research

Mass spectrometry (MS) represents an indispensable tool for the structural identification of natural products (NPs) and is one of the major focus areas of analytical chemistry research. The technique has long been used to obtain molecular weights and further molecular formulae. In the past, former ionization sources such as electronic impact (EI) limited MS analysis to predominately volatile, polar, and thermostable compounds. However, the development of soft ionization techniques such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and laser desorption/ionization (LDI) have gradually extended the scope of MS analysis to a much wider range of chemical entities. Moreover, the hyphenation of liquid and gas chromatography with MS (LC‐MS, GC‐MS) has provided a most powerful tool for the analysis of complex mixtures and NPs. In fact, LC‐MS is often considered as a method of first choice particularly when studying complex mixtures of small molecules. On the other hand, recent developments in matrix‐assisted laser desorption/ionization (MALDI) and LDI may provide useful supplements and potential alternatives to this approach. Both methods share similar, though slightly different ionization mechanisms. While MALDI uses small molecules comprising strong UV chromophores (matrices) to transfer laser energy to the sample material, LDI targets compounds that can be directly ionized by laser irradiation without any matrix support. Moreover, certain compounds showing LDI properties may also work as MALDI matrices. With regard to NPs research, MALDI and LDI may help overcoming certain limitations encountered in LC‐MS such as the indispensable use of buffer solutions when analyzing alkaloids. Moreover, as (MA)LDI hardly requires any sample conditioning, analysis time can be significantly shortened. With all this in mind, the subsequent article will highlight some interesting MALDI and LDI applications, which focus on the detection of NPs in complex mixtures. This includes the use of specifically adapted matrices for the selective detection of alkaloids (i), the study of the inherent LDI and matrix properties of phenolic compounds (ii) as well of evaluation on the reproducibility of LDI signal patterns (iii). Eventually, a statistical approach toward LDI profiling, which may provide a future tool for quality control of large sample batches will be presented (iv)

Atraumatic oral spray immunization with replication-deficient viral vector vaccines

The development of needle-free vaccines is one of the recently defined grand challenges in global health (H. Varmus, R. Klausner, R. Klausner, R. Zerhouni, T. Acharya, A. S. Daar, and P. A. Singer, Science 302:398-399, 2003). To explore whether a natural pathway to the inductive site of the mucosa-associated lymphatic tissue could be exploited for atraumatic immunization purposes, replication-deficient viral vector vaccines were sprayed directly onto the tonsils of rhesus macaques. Tonsillar immunization with viral vector vaccines encoding simian immunodeficiency virus (SIV) antigens induced cellular and humoral immune responses. Viral RNA levels after a stringent SIV challenge were reduced, providing a level of protection similar to that observed after systemic immunization with the same vaccines. Thus, atraumatic oral spray immunization with replication-deficient vectors can overcome the epithelial barrier, deliver the vaccine antigen to the mucosa-associated lymphatic tissue, and avoid induction of tolerance, providing a novel approach to circumvent acceptability problems of syringe and needle vaccines for children and in developing countries

Immunogenicity and efficacy of immunodeficiency virus-like particles pseudotyped with the G protein of vesicular stomatitis virus

Vaccination with exogenous antigens such as recombinant viral proteins, immunodeficiency virus-derived whole inactivated virus particles, or virus-like particles (VLP) has generally failed to provide sufficient protection in animal models for AIDS. Pseudotyping VLPs with the vesicular stomatitis virus G protein (VSV-G), which is known to mediate entry into dendritic cells, might allow more efficient stimulation of immune responses. Therefore, we pseudotyped noninfectious immunodeficiency virus-like particles with VSV-G and carried out a preliminary screen of their immunogenicity and vaccination efficacy. Incorporation of VSV-G into HIV-1 VLPs led to hundred-fold higher antibody titers to HIV-1 Gag and enhancement of T cell responses in mice. Repeated vaccination of rhesus monkeys for 65 weeks with VSV-G pseudotyped simian immunodeficiency virus (SIV)-like particles (VLP[G]) provided initial evidence for efficient suppression of viral load after mucosal challenge with the SIVmac239 virus. Challenge of monkeys after a 28 week vaccination regimen with VLP[G] led to a reduction in peak viremia, but persistent suppression of viral load was not achieved. Due to limitations in the number of animals available for this study, improved efficacy of VSV-G pseudotyped VLPs in nonhuman primates could not be demonstrated. However, mouse experiments revealed that pseudotyping of VLPs with fusion-competent VSV-G clearly improves their immunogenicity. Additional strategies, particularly adjuvants, should be considered to provide greater protection against a challenge with pathogenic immunodeficiency virus

Destination Management through Organizational Ambidexterity

Tourism can help regenerate post-colonial, post-conflict and post-disaster destinations (PCCDs), and national governments and destination marketing organisations (DMOs) play a central role in this. They face the dilemma of either consolidating tourism situations with seemingly safe, known, predictable steps, or taking more ambitious risk-prone, less tried-and-tested and more uncertain approaches. This choice can be portrayed as the respective exploitative and explorative dimensions of strategic conceptual framework of organisational ambidexterity (OA). This regional spotlight provides a conceptual analysis using the lens of OA to examine these dynamics. It focuses on the specific case of Haiti, set within the context of the Caribbean region. A range of OA effects in relation to tourist enclaves is identified. In particular, the spotlight argues for less segregation and separation between tourist and local populations, along with a need for DMOs to espouse more exploitative-explorative postures. In terms of wider implications, it can be argued that other Caribbean economies might learn lessons from the discussion of the Haitian case

New Developments of Laser Desorption Ionization Mass Spectrometry in Plant Analysis

The structural identification of natural products is one of the major focus areas of analytical chemistry research. Mass spectrometry (MS) has long been used to obtain molecular weights and further molecular formulae. In the past, former ionization sources such as electronic impact unfortunately limited MS analysis to predominately volatile, polar, and thermostable compounds. However, recent developments in soft ionization techniques such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), or laser desorption/ionization (LDI) have gradually extended MS analysis to a much wide range of chemical structures. As far as small natural compounds are concerned, LDI sources are still seldom used because of specific technical limitations. Indeed, the photoionization process of LDI is generally assisted by a matrix, which is a small molecule carrying strong UV chromophore. The process is then called matrix‐assisted laser desorption/ionization (MALDI) process. MALDI ionization therefore induces the formation of numerous matrix ions that commonly appear in the range 0–600 Da, and consequently interfere with molecular ions originating from many natural products. For this reason, the correct signal assignment is highly impaired in the critical region of interest. As LDI and MALDI are not only soft ionization processes but also quite sensitive techniques yielding high resolution spectra when coupled to a time‐of‐flight (TOF) analyzer, different attempts have been made to adapt these techniques for the analysis of natural products. Three of them will be more specifically discussed in this chapter: (i) LDI on neat gold surfaces obtained by physical vapor diffusion (PVD), (ii) desorption/ionization on self‐assembled monolayer surfaces (DIAMS), and (iii) the use of specific matrices for the selective detection of alkaloids

Studies on the reactivity of a tertiary allylic alcohol in an acetophenonic series, a model for natural products synthesis

The synthesis of benzopyranic simplified analogues of dibenzopyranic natural compounds is described, together with the access to a precursor of a new furobenzopyranic natural product. These natural products have anti-cancer activity. The 1,3-diacetoxy-2-acetyl-4-(3-hydroxy-3-methylbut-1-enyl)benzene synthone is used as a common precursor to these structures

New Use for a Compound as a Matrix in the Specific Detection, Identification and/or Quantification of Alkaloids by MALDI-TOF Mass Spectrometry

The present invention relates to (i) a method of analysing small molecules that may have a mass of < 800 Da, in particular alkaloids, said method being generally referred to as MALDI-TOF-MS (or MALDI Time-of-Flight MAss Spectrometry) which is an acronym for a method of analysis by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, to (ii) a molecule according to formula (I) and to the use thereof as a matrix in such an analysis method

Toxicity of neem oil to Bemisia tabaci biotype B nymphs reared on dry bean.

O objetivo deste trabalho foi determinar o estágio ninfal de Bemisia tabaci biótipo B mais suscetível ao óleo de nim (Azadirachta indica A. Juss.) aplicado em feijoeiro (Phaseolus vulgaris L.), em casa telada. Foram avaliados o tempo letal (TL) e concentração letal (CL) do óleo comercial de sementes de nim Dalneem. Para CL, concentrações de 0, 0,1, 0,25, 0,5, 1 e 2% do produto foram pulverizadas diretamente sobre as ninfas em cada ínstar. Para TL, o produto foi avaliado a 0, 0,5 e 1% de óleo de nim em cada ínstar. Ninfas vivas e mortas foram contadas cinco dias após a pulverização para CL e diariamente para TL durante seis dias. Para o quarto ínstar, a CL50 foi de 0,56% de óleo de nim. Considerando todos os ínstares, CL50 e CL95 foram estimadas em 0,32 e 2,78% de óleo de nim, respectivamente. Os TL50 para 1% de nim foram estimados em 2,46, 4,45, 3,02 e 6,98 dias para o primeiro, segundo, terceiro e quarto ínstares, respectivamente. Os TL50 estimados para 0,5 e 1% de óleo de nim foram de cinco e quatro dias, respectivamente, considerando todos os ínstares. No sexto dia, foi observada mortalidade superior a 80% para o primeiro, segundo e terceiro ínstares a 1% de óleo de nim. Os três primeiros ínstares foram mais suscetíveis ao óleo de nim que o quarto ínstar