G-quadruplex DNA (G4-DNA) structures are four-stranded helical DNA (or RNA) structures, comprising stacks of G-tetrads, which are the outcome of planar association of four guanines in a cyclic Hoogsteen hydrogen-bonding arrangement. In the last decade the number of publications where CD spectroscopy has been used to study G4-DNAs, is extremely high. However, with very few exceptions, these investigations use an empirical interpretation of CD spectra. In this interpretation two basic types of CD spectra have been associated to a single specific difference in the features of the strand folding, i.e. the relative orientation of the strands, "parallel" (all strands have the same 5' to 3' orientation) or "antiparallel". Different examples taken from the literature where the empirical interpretation is not followed or is meaningless are presented and discussed. Furthermore, the case of quadruplexes formed by monomeric guanosine derivatives, where there is no strand connecting the adjacent quartets and the definition parallel/antiparallel strands cannot apply, will be discussed. The different spectral features observed for different G-quadruplexes is rationalised in terms of chromophores responsible for the electronic transitions. A simplified exciton coupling approach or more refined QM calculations allow to interpret the different CD features in terms of different stacking orientation (head-to-tail, head-to-head, tail-to-tail) between adjacent G-quartets irrespectively of the relative orientation of the stands (parallel/antiparallel).

Self-assembly plays an important role in the formation of many chiral biological structures and in the preparation of chiral functional materials. Therefore the control of chirality in synthetic or biological self-assembled systems is important either for the comprehension of recognition phenomena or to obtain materials with predictable and controllable properties. Circular dichroism was developed to study molecular chirality, however, because of its outstanding sensitivity to chiral perturbations of the system under investigation; it has been extended more recently to supramolecular chemistry. In particular, self-assembly processes leading to the formation of chiral supramolecular architectures (and eventually to gels or liquid crystal phases) can be monitored by CD. Furthermore, CD spectroscopy often allows one to obtain structural information on the assembled structures. This review deals with representative contributions to the study of supramolecular chirality by means of circular dichroism.

A randomized controlled trial was performed to compare the short-term effectiveness of botulinum toxin injections and physiatric treatment provided by means of Fascial Manipulation techniques in the management of myofascial pain of jaw muscles. Thirty patients with a Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) diagnosis of myofascial pain were randomized to receive either single-session botulinum toxin injections (Group A) or multiple-session Fascial Manipulation (Group B). Maximum pain levels (VAS ratings) and jaw range of motion in millimeters (maximum mouth opening, protrusion, right and left laterotrusion) were assessed at baseline, at the end of treatment, and at a three-month follow-up. Both treatment protocols provided significant improvement over time for pain symptoms. The two treatments seem to be almost equally effective, Fascial Manipulation being slightly superior to reduce subjective pain perception, and botulinum toxin injections being slightly superior to increase jaw range of motion. Differences between the two treatment protocols as to changes in the outcome parameters at the three-months follow-up were not relevant clinically. Findings from the present investigation are in line with literature data supporting the effectiveness of a wide spectrum of conservative treatment approaches to myofascial pain of the jaw muscles. Future studies on larger samples over a longer follow-up span are needed on the way to identify tailored treatment strategies.

When a chiral dopant is dissolved in an achiral liquid crystal medium, the whole sample organizes into a helical structure with a characteristic length-scale of the order of microns. The relation between chirality at these quite different length-scales can be rationalized by a relatively simple model, which retains the relevant factors coming into play: the molecular shape of the chiral dopant, which controls the chirality of short range intermolecular interactions, and the elastic properties of the nematic environment, which control the restoring torques opposing distortion of the director. In this tutorial review the relation between molecular and phase chirality will be reviewed and several applications of the chiral doping of nematic LCs will be discussed. These range from the exploitation of the amplified molecular chirality for stereochemical purposes (e.g., the determination of the absolute configuration or the enantiomeric excess), to newer applications in physico-chemical fields. The latter take advantage of the periodicity of the chiral field, with length-scales ranging from hundreds to thousands of nanometres, which characterise the cholesteric phase.

The lipophilic nucleoside 3‘,5‘-didecanoyl-2‘-deoxyguanosine, dG 1, extracts potassium salts from water into organic solvents. The K+ extraction drives the self-association of dG 1 to give G-quartet structures. A series of 1H NMR experiments indicates that the identity of the assembled species in CDCl3 is modulated by the amount of K+ extracted by dG 1. At an 8:1 dG 1 to K+ picrate ratio, the octamer (dG 1)8−K+ predominates in solution. The (dG 1)8−K+ supramolecular complex, formed by coordination of a single K+ ion by eight dG 1 monomers, is robust and structurally unique. The 1H NMR chemical shifts for both the exchangeable and nonexchangeable protons of (dG 1)8−KI in CDCl3 were assigned from a combination of 2D 1H−1H and 13C−1H correlation experiments. One set of 1H NMR signals corresponds to a dG 1 nucleoside with an anti conformation about the C(1‘)−N(9) glycosidic bond, whereas the other set of signals is due to 50% of the didecanoyl dG 1 adopting a syn conformation. Although the possible arrangements of an octamer containing a 1:1 ratio of anti dG 1 to syn dG 1 are many, the present NMR analysis leads to a defined single species composed of two G-quartets. In one tetramer, all of the dG 1 components have a syn conformation about the C(1‘)−N(9) glycosidic bond, while the other tetramer has an “all-anti” conformation. Moreover, intertetramer NOEs are consistent with stacking of the “all-anti” tetramer in a “head-to-tail” orientation on top of the “all-syn” tetramer, thus sandwiching a central K+ ion. This solution structure is, to our knowledge, different from all of the assembled structures described so far for guanine aggregates. Presumably, the K+-bound octamer represents the first observable stage of the assembly process in the aggregation of dG 1.