Volume 4, Issue 6 -

The power of GC/MS to resolve, characterise and quantify complex mixtures of organic compounds with high sensitivity has made it an indispensable analytical tool to address detailed questions about the chemical constituents of works of art. This paper provides an overview of the technique and its particular suitability to material studies of art and historical artefacts, and reviews its diverse research applications concerning the organic composition of artists’ and conservation materials. Options with regard to sample preparation by chemical derivatisation, pyrolysis techniques, and methods for the analysis of volatile organic compounds are discussed, as well as various approaches to the treatment and interpretation of data. The greatest value is gained from GC/MS when it is used as a complementary technique, informed by and in synergy with other methods of analysis.

This chapter focuses on computational techniques for identifying and optimizing lead molecules, with a special emphasis on natural compounds. A number of case studies have been specifically discussed, such as the case of the naphthyridine scaffold, discovered through a structure-based virtual screening (SBVS) and proposed as the starting point for further lead optimization process, to enhance its telomeric RNA selectivity. Another example is the case of Liphagal, a tetracyclic meroterpenoid extracted from Aka coralliphaga , known as PI3Kα inhibitor, provide an evidence for the design of new active congeners against PI3Kα using molecular dynamics (MD) simulations. These are only two of the numerous examples of the computational techniques’ powerful in drug design and drug discovery fields. Finally, the design of drugs that can simultaneously interact with multiple targets as a promising approach for treating complicated diseases has been reported. An example of polypharmacological agents are the compounds extracted from mushrooms identified by means of molecular docking experiments. This chapter may be a useful manual of molecular modeling techniques used in the lead-optimization and lead identification processes.

Recent developments in polyoxometalate photochemistry are discussed with a focus on visible light driven productive chemical reactions. Special attention is given to the fundamental photochemistry of polyoxometalates and the effects on the resulting photoprocesses.

Databases play an important role in various computational techniques, including virtual screening (VS) and molecular modeling in general. These collections of molecules can contain a large amount of information, making them suitable for several drug discovery applications. For example, vendor, bioactivity data or target type can be found when searching a database. The introduction of these data resources and their characteristics is used for the design of an experiment. The description of the construction of a database can also be a good advisor for the creation of a new one. There are free available databases and commercial virtual libraries of molecules. Furthermore, a computational chemist can find databases for a general purpose or a specific subset such as natural products (NPs). In this chapter, NP database resources are presented, along with some guidelines when preparing an NP database for drug discovery purposes.

This contribution reports on the theoretical foundations of Raman spectroscopy. Since the discovery of the Raman effect in 1928, Raman spectroscopy with its linear and nonlinear variants has established itself as a powerful analytical tool in almost all scientific fields (chemistry, physics, material sciences, pharmacy, biology, (bio)medicine, geology, mineralogy, environmental sciences, etc.). First, a short introduction to linear Raman spectroscopy is given, followed by two approaches to increase the intrinsically weak Raman signal, namely resonance Raman and surface enhanced Raman spectroscopy. The last part of this contribution briefly introduces nonlinear Raman processes observed using pulsed lasers as excitation sources.

Natural products are also called secondary metabolites to distinguish them from the primary metabolites, i.e. those natural compounds like glucose, amino acids, etc. that are present in every living cell and are used and required in the essential life processes of cells. Natural products are classified according to their metabolic building blocks into alkaloids, fatty acids, polyketides, phenyl propanoids and aromatic polyketides, and terpenoids. The structural diversity of natural products is explored using the scaffold approach focusing on the characteristic carbon frameworks.  Aside from discussing specific alkaloids that are either pharmacologically (e.g. boldine, berberine, galantamine, etc.) or historically (caffeine, atropine, lobeline, etc.) important alkaloids, a single chart is presented which shows the typical scaffolds of the most important subclasses of alkaloids.  How certain classes of natural products are formed in nature from simple biochemical ‘building blocks’ are shown using graphical schemes. This has been done for a typical tetra-ketide (6-methylsalicylic acid) from acetyl coenzyme A, or in general to all the major subclasses of terpenes.   An important aspect of understanding the structural diversity of natural products is to recognize how some compounds can be visualized as key intermediates for enzyme mediated transformation to several other related structures.  This is seen in the case of how arachidonic acid can transform into prostaglandins, or geranyl diphosphate to various monoterpenes, or squalene epoxide to various pentacyclic triterpenes, or cholesterol transforming to sex hormones, bile acids and the cardioactive cardenolides and bufadienolides. These are presented in carefully designed schemes and charts that are appropriately placed in the relevant sections of the narrative texts.  The ecological functions and pharmacological properties of natural products are also presented showing wherever possible how the chemical scaffolds have led to developing drugs as well as commercial products like sweeteners.

Micro Raman spectroscopy has been applied very early in environmental analytics. However, until now the field of application is quite limited. The main reasons for the low acceptance are high cost of the method and the low throughput. New developments in technology lead to cheaper instrumentation. Automation of Raman microscopy of particles might be a solution for a higher throughput and a broader application in environmental analytics. A more detailed analysis of aerosols and microplastic is good examples that could benefit from this development.

Metallic and bimetallic nanosponges with well-defined size and form have attracted increasing attention due to their unique structural properties and their potential for many applications. In this chapter, the recently developed methods for the synthesis and preparation of metallic and bimetallic nanosponges are presented. These methods can be mainly cataloged in two groups: dealloying-based methods and reduction reaction-based methods. Different topographical reconstruction methods for the investigation of their structural properties are then reviewed briefly. The optical properties of the metallic nanosponges are clearly different from those of the solid counterparts due to the tailored disordered structure. The recent advances in the exploration of the distinct linear and non-linear optical properties of the nanosponges are summarized. Graphical Abstract :