A Combined Infrared and Computational Study of Gas-Phase Mixed-Ligand Rhodium Complexes: Rh(CO)n(N2O)m+ (n = 1-5, m = 1-4).

In this study, mixed carbonyl and nitrous oxide complexes with Rh+ were studied by mass-selective infrared photodissociation spectroscopy in a molecular beam. The infrared spectra, recorded in the region of the CO and N2O N═N stretches, were assigned and interpreted with the aid of simulated spectra of low-energy structural isomers. Clear evidence of an inner coordination shell of four ligands is observed. The observed vibrational structure can be understood on the basis of local mode vibrations in the two ligands. However, there is also evidence of multiple low-lying isomers and cooperative binding effects between the two ligands. In particular, σ donation from directly coordinated nitrous oxide ligands drives more classical carbonyl bonding than has been observed in pure carbonyl complexes. The observed fragmentation branching ratios following resonant infrared absorption are explained by simple statistical and energetic arguments, providing a contrast with those of equivalent Au+ complexes.

Closing the Shell: Gas-Phase Solvation of Halides by 1,3-Butadiene.

Gas-phase solvation of halides by 1,3-butadiene has been studied via a combination of photoelectron spectroscopy and density functional theory. Photoelectron spectra for X- ⋯(C4 H6 )n (X=Cl, Br, I where n=1-3, 1-3 and 1-7 respectively) are presented. For all complexes, the calculated structures indicate that butadiene is bound in a bidentate fashion through hydrogen-bonding, with the chloride complex showing the greatest degree of stabilisation of the internal C-C rotation of cis-butadiene. In both Cl- and Br- complexes, the first solvation shell is shown to be at least n = 4 ${n = 4}$ from the vertical detachment energies (VDEs), however for I- , increases in the VDE may suggest a metastable, partially filled, first solvation shell for n = 4 ${n = 4}$ and a complete shell at n = 6 ${n = 6}$ . These results have implications for gas-phase clustering in atmospheric and extraterrestrial environments.

Hydrogen Bonding versus Halogen Bonding: Spectroscopic Investigation of Gas-Phase Complexes Involving Bromide and Chloromethanes.

Hydrogen bonding and halogen bonding are important non-covalent interactions that are known to occur in large molecular systems, such as in proteins and crystal structures. Although these interactions are important on a large scale, studying hydrogen and halogen bonding in small, gas-phase chemical species allows for the binding strengths to be determined and compared at a fundamental level. In this study, anion photoelectron spectra are presented for the gas-phase complexes involving bromide and the four chloromethanes, CH3 Cl, CH2 Cl2 , CHCl3 , and CCl4 . The stabilisation energy and electron binding energy associated with each complex are determined experimentally, and the spectra are rationalised by high-level CCSD(T) calculations to determine the non-covalent interactions binding the complexes. These calculations involve nucleophilic bromide and electrophilic bromine interactions with chloromethanes, where the binding motifs, dissociation energies and vertical detachment energies are compared in terms of hydrogen bonding and halogen bonding.

An Infrared Study of Gas-Phase Metal Nitrosyl Ion-Molecule Complexes.

We present a combined experimental and quantum chemical study of gas-phase group 9 metal nitrosyl complexes, M(NO)n+ (M = Co, Rh, Ir). Experimental infrared photodissociation spectra of mass-selected ion-molecule complexes are presented in the region 1600 cm-1 to 2000 cm-1 which includes the NO stretch. These are interpreted by comparison with the simulated spectra of energetically low-lying structures calculated using density functional theory. A mix of linear and nonlinear ligand binding is observed, often within the same complex, and clear evidence of coordination shell closing is observed at n = 4 for Co(NO)n+ and Ir(NO)n+. Calculations of Rh(NO)n+ complexes suggest additional low-lying five-coordinate structures. In all cases, once a second coordination shell is occupied, new spectral features appear which are assigned to (NO)2 dimer moieties. Further evidence of such motifs comes from differences in the spectra recorded in the dissociation channels corresponding to single and double ligand loss.

Halide-propene complexes: validated DSD-PBEP86-D3BJ calculations and photoelectron spectroscopy.

Anion photoelectron spectroscopy has been used to determine the electron binding energies of the X-⋯C3H6 (X = Cl, Br, I) complexes. To complement the experimental spectra the DSD-PBEP86-D3BJ functional has been employed, following comparison with previously calculated halide/halogen-molecule van der Waals complexes. To validate the functional, comparison between the complex geometries and vertical detachment energies with both experimental and CCSD(T)/CBS data for a suite of halide-molecule complexes is also made. PES spectra determine the electron binding energies as 3.89 eV and 4.00 eV, 3.59 eV and 4.01 eV, and 3.26 eV and 4.20 eV for transitions to perturbed 2P states of the chlorine, bromine and iodine complexes respectively. Two contributing structures resulting in the photoelectron spectrum are those where the halide is coordinated by two hydrogens, each from a terminal carbon in C3H6, and when bifurcating the CC bond. These complexes are distinct from the corresponding halide-ethene complexes and represent potential entry pathways to haloakyl radical formation in atmospheric and extraterrestrial environments.

A tale of two conformers: spectroscopic evidence for halide catalysed formic acid isomerisation.

Halide-formic acid complexes have been studied utilising a combined experimental and theoretical approach. Formic acid exists as two conformers, distinguished by the relative rotation about the C-OH bond. Computational investigation of the formic acid isomerisation reaction between the two conformers has revealed the ability of halide anions to catalyse the formation of, and preferentially stabilise, the higher energy conformer. Anion photoelectron spectroscopy has been used to study the halide-formic acid complexes, with the experimental vertical detachment energies compared with simulated photodetachment energies with respect to halide complexes with both formic acid conformers. The existence of experimental spectral features associated with halide complexes of the higher energy formic acid confomer confirms in situ generation, likely as a result of the halide mediated catalytic formation.

Spectroscopic Study of the Br- +CH3 I→I- +CH3 Br SN 2 Reaction.

Mass spectrometry and anion photoelectron spectroscopy have been used to study the gas-phase S N 2 ${{{\rm S}}_{{\rm N}}2}$ reaction involving B r - ${{{\rm B}{\rm r}}^{-}}$ and C H 3 I ${{{\rm C}{\rm H}}_{3}{\rm I}}$ . The anion photoelectron spectra associated with the reaction intermediates of this S N 2 ${{{\rm S}}_{{\rm N}}2}$ reaction are presented. High-level CCSD(T) calculations have been utilised to investigate the reaction intermediates that may form as a result of the S N 2 ${{{\rm S}}_{{\rm N}}2}$ reaction along various different reaction pathways, including back-side attack and front-side attack. In addition, simulated vertical detachment energies of each reaction intermediate have been calculated to rationalise the photoelectron spectra.

Photoelectron Spectroscopy and High-Level Ab Initio Calculations of the Iodide-Methylperoxy Radical Complex.

Anion photoelectron spectroscopy has been used to investigate the structure and dynamics of CH3OOI- van der Waals complexes. Peaks within the photoelectron spectrum are attributed to photodetachment to the perturbed 2P3/2 state of I···CH3OO (3.46 eV) and the two 2P states of bare iodine. A broad feature at 1.7-2.4 eV is attributed to detachment to the excited singlet states from two O2-···CH3I complexes. This represents the first anion photoelectron spectroscopy of a halide-bound methylperoxy radical species. Complex structures have been optimized using MP2/aug-cc-pVQZ with single-point energies at W1w theory for ground-state complexes and NEVPT2 for photodetachment to excited O2. Interactions are dominated by electrostatics, with the anion species interacting with the methyl pocket of the solvating molecule, suggesting conversion via an SN2 mechanism, and excess energy leading to complex dissociation within the timescale of mass spectrometry. The calculated W1w Gibbs energies suggest that while an electron transfer (ET) pathway to conversion is available, it is comparatively unfavored.

Towards an Understanding of Halide Interactions with the Carbonyl-Containing Molecule CH3 CHO.

The anion photoelectron spectra of Cl- ⋅⋅⋅CD3 CDO, Cl- ⋅⋅⋅(CD3 CDO)2 , Br- ⋅⋅⋅CH3 CHO, and I- ⋅⋅⋅CH3 CHO are presented with electron stabilisation energies of 0.55, 0.93, 0.48, and 0.40 eV, respectively. Optimised geometries of the singly solvated species featured the halide appended to the CH3 CHO molecule in-line with the electropositive portion of the C=O bond and having binding energies between 45 and 52 kJ mol-1 . The doubly solvated Cl- ⋅⋅⋅(CH3 CHO)2 species features asymmetric solvation upon the addition of a second CH3 CHO molecule. Theoretical detachment energies were found to be in excellent agreement with experiment, with comparisons drawn between other halide complexes with simple carbonyl molecules.

Spectroscopic Investigation of Chalcogen Bonding: Halide-Carbon Disulfide Complexes.

A combined experimental and theoretical approach has been used to study intermolecular chalcogen bonding. Specifically, the chalcogen bonding occurring between halide anions and CS2 molecules has been investigated using both anion photoelectron spectroscopy and high-level CCSD(T) calculations. The relative strength of the chalcogen bond has been determined computationally using the complex dissociation energies as well as experimentally using the electron stabilisation energies. The anion complexes featured dissociation energies on the order of 47 kJ/mol to 37 kJ/mol, decreasing with increasing halide size. Additionally, the corresponding neutral complexes have been examined computationally, and show three loosely-bound structural motifs and a molecular radical.

Photoelectron Spectroscopy and Structures of X- ⋠⋠⋠CH2 O (X=F, Cl, Br, I) Complexes.

A combined experimental and theoretical approach has been used to investigate X- ⋅⋅⋅CH2 O (X=F, Cl, Br, I) complexes in the gas phase. Photoelectron spectroscopy, in tandem with time-of-flight mass spectrometry, has been used to determine electron binding energies for the Cl- ⋅⋅⋅CH2 O, Br- ⋅⋅⋅CH2 O, and I- ⋅⋅⋅CH2 O species. Additionally, high-level CCSD(T) calculations found a C2v minimum for these three anion complexes, with predicted electron detachment energies in excellent agreement with the experimental photoelectron spectra. F- ⋅⋅⋅CH2 O was also studied theoretically, with a Cs hydrogen-bonded complex found to be the global minimum. Calculations extended to neutral X⋅⋅⋅CH2 O complexes, with the results of potential interest to atmospheric CH2 O chemistry.

Wnt and Neuregulin1/ErbB signalling extends 3D culture of hormone responsive mammary organoids.

The development of in vitro culture systems quantitatively and qualitatively recapitulating normal breast biology is key to the understanding of mammary gland biology. Current three-dimensional mammary culture systems have not demonstrated concurrent proliferation and functional differentiation ex vivo in any system for longer than 2 weeks. Here, we identify conditions including Neuregulin1 and R-spondin 1, allowing maintenance and expansion of mammary organoids for 2.5 months in culture. The organoids comprise distinct basal and luminal compartments complete with functional steroid receptors and stem/progenitor cells able to reconstitute a complete mammary gland in vivo. Alternative conditions are also described that promote enrichment of basal cells organized into multiple layers surrounding a keratinous core, reminiscent of structures observed in MMTV-Wnt1 tumours. These conditions comprise a unique tool that should further understanding of normal mammary gland development, the molecular mechanism of hormone action and signalling events whose deregulation leads to breast tumourigenesis.

Halide-Nitrogen Gas-Phase Clusters: Anion Photoelectron Spectroscopy and High Level ab Initio Calculations.

The gas phase anion photoelectron spectra are presented for the halide-nitrogen clusters X(-)···(N2)n, where X = Br and I and n ≤ 5. Electron binding energies for each cluster in the halide series are determined, with no evidence observed for first solvation shell closure in either series. High level ab initio calculations at the CCSD(T) level of theory are presented for the anion and neutral halogen-nitrogen complexes. For the anion species, two minima are predicted corresponding to a loosely bound C2v "T-shaped" species and to a higher energy covalently bound "triangle" C2v symmetry geometry. For the neutral species, three stationary points were located, two of which display similar form to the anion minima and a third which is linear, i.e., C∞v symmetry. The "T-shaped" geometry is a transition state linking equivalent C∞v symmetry minima. Cluster dissociation energies (D0) were determined, for both anion and neutral global minima at the CCSD(T) complete basis set limit, to be 7.8 kJ mol(-1) and 7.0 kJ mol(-1) and 3.5 kJ mol(-1) and 5.0 kJ mol(-1) for the bromine and iodine species, respectively.

Visualizing Actin Architectures in Cells Incubated with Cell-Penetrating Peptides.

Defining the exact role of the actin cytoskeleton in mediating endocytosis through different pathways is a significant challenge. The general consensus is that actin has an important role in organizing the early stages of endocytosis but there is still much to learn. Actin has also been implicated in cell internalization of cell-penetrating peptides (CPPs). It is suggested that CPP variants such as octaarginine (R8) and the HIV Tat peptide induce actin-dependent plasma membrane perturbation and enter via macropinocytosis. Here, we describe confocal microscopy techniques that allow for high-resolution spatial characterization of the actin cytoskeleton in untreated mammalian cells and those incubated with actin-disrupting agents and CPPs. By performing X-Y-Z projection images through different regions of cells to show basal and apical profiles, we initially highlight how these techniques can be used to reveal major differences in cortical and filamentous actin organization between different cell lines. Using these techniques, we demonstrate that the actin-disrupting agent cytochalasin D rapidly changes this framework at concentrations significantly lower than is normally used. Experiments are also performed to highlight that serum starvation significantly sensitizes cells to the effects of R8 on actin-induced ruffling and lamellapodia formation. The techniques described here can be used to gain a higher level of knowledge of the organization of the actin network in individual model cell systems, how this is perturbed using commonly used actin inhibitors, and how plasma membrane reorganization can be induced by the addition of drug delivery vectors such as CPPs.

Different photochemical events of a genetically encoded phenyl azide define and modulate GFP fluorescence.

Expanding the genetic code opens new avenues to modulate protein function in real time. By genetically incorporating photoreactive phenyl azide, the fluorescent properties of green fluorescent protein (GFP) can be modulated by light. Depending on the residue in GFP programmed to incorporate the phenyl azide, different effects on function and photochemical pathways are observed.

Endocytosis, intracellular traffic and fate of cell penetrating peptide based conjugates and nanoparticles.

The insides of cells can be viewed as a treasure trove of targets for therapeutic intervention of diseases or as deposits for contrasting agents. Increasingly the molecules that need to be delivered to the inside of cells for these purposes are macromolecular and membrane impermeable. Cell penetrating peptides (CPPs) have proven abilities to deliver a range of macromolecular cargo into cells thus raising their profile as potential delivery vectors for wide-ranging applications. There is evidence to suggest that CPPs first enter cells through endocytosis and that cytosolic delivery is mediated across endolysosomal membranes. Their capacity to do this, over direct plasma membrane translocation, is likely to depend on the nature and size of the cargo. Cells use a range of endocytic routes to facilitate entry from well characterised pathways regulated by clathrin to more recently discovered and less characterised pathways regulated by clathrin independent mechanisms. These are likely to determine the intracellular fate of cell delivery vectors including those based on cell penetrating peptides. Thus gaining accurate knowledge of their endocytic uptake and traffic is an important characterisation criteria for progress in this field. This review describes the different endocytic pathways that have been identified in mammalian cells and specific reports that have studied the uptake mechanisms and endocytic traffic of cell penetrating peptides and their associated cargo. These cargoes range from short peptides to an increasing library of nanoparticles such as quantum dots, liposomes and polymeric dendrimers. The studies highlight the effectiveness of cell penetrating peptides for delivering these entities into a diverse array of cell types using different endocytic pathways. This is shown using microscopy based colocalisation analysis with the few specific endocytic probes available, and chemical inhibitors of endocytosis that suffer from lack of specificity. Overall, more specific probes, inhibitors and novel technologies are required for accurate characterisation of cellular dynamics of cell penetrating peptide conjugates thus allowing them to reach their full potential as vectors for therapeutics and other payloads.

Seeking professional help for mental health problems, among New Zealand secondary school students.

OBJECTIVE: Our aim was to investigate whether secondary school students with mental health problems sought help from general practitioners and to investigate whether mental illness type, socio-demographic variables, family, school and community factors were associated with seeking help. METHOD: A randomly selected sample of 9699 secondary school students from across New Zealand participated in the Youth2000 Health and Wellbeing Survey. Data analysis included uni-variate and regression analyses. RESULTS: Having symptoms of anxiety (p<0.0001), depression (p<0.0001), and suicidal thoughts (p<0.0001) were associated with help seeking. However, 82%of students who had significant mental health problems had not sought help from a general practitioner. Rates of help seeking increased with age for girls and decreased with age for boys. Seeking help for mental health problems was also associated with living in a single parent family (p<0.0001), living in an over-crowded house (p=0.0006), and being well known by a teacher (p=0.0004). CONCLUSIONS: The majority of New Zealand secondary school students with mental health problems do not obtain the help they need from general practitioners. Given the prevalence of mental health problems, it is important to find ways of identifying adolescents with difficulties and encouraging them to seek help.

Family influences, acculturation, and the prevalence of tobacco smoking among Asian youth in New Zealand: findings from a national survey.

The associations among family factors, acculturation, and the risk of regular smoking among Asian youth were investigated in a nationally representative survey in New Zealand. The strong relationships between protective family factors and lower risks of smoking were not attenuated in the presence of indicators suggestive of acculturation.

Hand-held internet tablets for school-based data collection.

BACKGROUND: In the last 20 years, researchers have been using computer self-administered questionnaires to gather data on a wide range of adolescent health related behaviours. More recently, researchers collecting data in schools have started to use smaller hand-held computers for their ease of use and portability. The aim of this study is to describe a new technology with wi-fi enabled hand-held internet tablets and to compare adolescent preferences of laptop computers or hand-held internet tablets in administering a youth health and well-being questionnaire in a school setting. METHODS: A total of 177 students took part in a pilot study of a national youth health and wellbeing survey. Students were randomly assigned to internet tablets or laptops at the start of the survey and were changed to the alternate mode of administration about half-way through the questionnaire. Students at the end of the questionnaire were asked which of the two modes of administration (1) they preferred, (2) was easier to use, (3) was more private and confidential, and (4) was easier to answer truthfully. RESULTS: Many students expressed no preference between laptop computers or internet tablets. However, among the students who expressed a preference between laptop computers or internet tablets, the majority of students found the internet tablets more private and confidential (p < 0.001) and easier to answer questions truthfully (p < 0.001) compared to laptop computers. CONCLUSION: This study demonstrates that using wi-fi enabled hand-held internet tablets is a feasible methodology for school-based surveys especially when asking about sensitive information.

Injury risk behaviours among young Asian New Zealanders: a national survey of secondary school students.

OBJECTIVE: To investigate injury risk behaviours among young Asian New Zealanders. METHOD: Secondary analysis of data from Youth2000, a nationwide cross-sectional youth health survey conducted in 2001 in a random sample of New Zealand (NZ) secondary schools using a multimedia, computer-assisted, self-administered interview. Of the 9,567 survey participants (aged 12 to 18 years), this study was restricted to students who identified with an 'Asian' ethnic category (n=922). RESULTS: Many young Asian New Zealanders report engaging in injury risk behaviours, including: not using helmets when cycling; dangerous drink and drug driving; and being intentionally physically harmed by others. NZ-born Asian students are more likely than overseas-born Asian students to report most of these risky behaviours. Chinese and Indian students are less likely to engage in most of these behaviours than their NZ European peers. CONCLUSION: While young Asian New Zealanders are a relatively healthy population, many engage in well-recognised injury risk behaviours. The lower levels of these risky behaviours in Indian and Chinese students compared with NZ European students, and the positive dose-response effect seen in relation to duration of residence in NZ, are likely to be due to the effect of acculturation. IMPLICATIONS: Injury prevention strategies for young people in NZ need to specifically consider the diversity, context and specific risk profiles of young Asian New Zealanders. Health promotion efforts for this group should target the use of safety equipment and risky driving behaviours and consider traditional cultural practices that may be protective.