Customization vs. standardization in global hotel expansion

There are numerous challenges that an international hotel chain faces when opening a property in a foreign country. The company’s response to those challenges will determine the new hotel’s overall success rate. This will in turn directly affect the corporation’s profit levels. The critical issue of this project is to define to what extent the world’s largest hotel chains utilize the theories of customization and standardization when designing a business strategy for a new property. In order to truly grasp the concept, it is essential for one to value the importance of brand standard in regards to globalization in the hospitality industry. By establishing solid company standards, each hotel chain develops its own brand name. Proper analysis of brand value will contribute to the development of an efficient marketing mix each time a hotel chain considers opening a new property in another country. The focus of the project is primarily on the luxury market segment. There are only a handful of hotel brands that belong to that category: Four Seasons, Ritz Carlton (Marriott), InterContinental and Crown Plaza (ICH Group), Hilton, Hyatt (Park Hyatt and Grand Hyatt), Mandarin Oriental, Sofitel, and Starwood (W, St. Regis, Sheraton and Luxury Collection). The majority of the world’s largest hotel corporations have multiple brands in their portfolios. For instance, Marriott Corporation owns and operates 15 different hotel brands. As a general rule, whether hotel corporations will decide to standardize or customize their services and products when expanding globally is based on an analysis of different levels of business and operational factors

Motion and Flexibility in Human Cytochrome P450 Aromatase

The crystal structures of human placental aromatase in complex with the substrate androstenedione and exemestane have revealed an androgen-specific active site and the structural basis for higher order organization. However, X-ray structures do not provide accounts of movements due to short-range fluctuations, ligand binding and protein-protein association. In this work, we conduct normal mode analysis (NMA) revealing the intrinsic fluctuations of aromatase, deduce the internal modes in membrane-free and membrane-integrated monomers as well as the intermolecular modes in oligomers, and propose a quaternary organization for the endoplasmic reticulum (ER) membrane integration. Dynamics of the crystallographic oligomers from NMA is found to be in agreement with the isotropic thermal factors from the X-ray analysis. Calculations of the root mean square fluctuations of the C-alpha atoms from their equilibrium positions confirm that the rigid-core structure of aromatase is intrinsic regardless of the changes in steroid binding interactions, and that aromatase self-association does not deteriorate the rigidity of the catalytic cleft. Furthermore, NMA on membrane-integrated aromatase shows that the internal modes in all likelihood contribute to breathing of the active site access channel. The collective intermolecular hinge bending and twisting modes provide the flexibility in the quaternary association necessary for membrane integration of the aromatase oligomers. Taken together, fluctuations of the active site, the access channel, and the heme-proximal cavity, and a dynamic quaternary organization could all be essential components of the functional aromatase in its role as an ER membrane-embedded steroidogenic enzyme

Biophysical studies of cytochrome P450 enzymes - biomimetic membranes as platforms to study protein-protein interactions

The structure of a cellular membrane is a complex amalgamation of the phospholipid bilayer and proteins that reside in it; i.e. ion-channels, enzymes, G protein-coupled receptors, to name a few. The role of the membrane in cellular function and homeostasis has been long recognised; however, studies of proteins that reside in it are inconvenienced by the lack of enough purified native protein to allow classical crystallographic and spectroscopic examination. The advent of surface-based techniques that require only a small amount of protein and allow biomimetic membrane deposition, provide new avenues to study these proteins, their interactions with the membrane and protein-protein interaction that occur in the membrane. This thesis employs the quartz crystal microbalance with dissipation monitoring (QCM-D) technique to study peptide and protein interactions with the biomimetic membranes. QCM-D provides the suitable surface that can be modified with the membrane and can record changes over time that occur upon protein or peptide binding. Furthermore, QCM-D can monitor rearrangements and fluctuations in the viscoelastic properties of the resulting composite layers, which is not possible to do with any other technique. This technique enabled a study of the mechanisms of membrane disruption by lytic antimicrobial peptides, needed for novel drugs to treat multi-resistant bacterial infections. Also, the protein-protein interactions which are important in the function of steroidogenic enzymes residing in the endoplasmic reticulum membrane were investigated. Prior to the study of peptides and proteins interacting with the biomimetic membranes, it was first necessary to characterise the deposition processes of the biomimetic membrane on the gold coated QCM sensor surface. Deposition and membrane formation from liposome solutions onto the gold-coated QCM sensor surface, that was first modified with the self-assembled monolayer (SAM) of mercaptopropionic acid, was investigated, and the results of these studies are presented in Chapter 2 (Paper 1). Once the membrane deposition was developed as a reproducible protocol, the interaction of a family of antimicrobial peptides was studied with different biomimetic membranes, and the results of these experiments are presented in Chapter 3 (Papers 2 and 3). These antimicrobial peptides were chosen for initial studies of membrane disruption in order to better understand and optimise the QCM-D technique before attempting to investigate interactions of proteins with the biomimetic membranes. Additionally, three more papers, that are not included in the main thesis body, also involve experiments of this kind that were undertaken during this project, and are included in the appendices. Development of a methodology to investigate protein-protein interactions using QCM-D necessitated the investigation of a single protein adsorption onto the gold-coated QCM chips modified with octanethiol-SAM. This was followed by adsorption studies of more complex system involving a bacterial cytochrome P450 enzyme and its partner proteins on various SAMs. This study was able to answer important questions about the surface interactions of these proteins. Results of these studies are presented in Chapter 4 (Paper 4 and section 4.2). Ultimately, Chapter 5 describes the investigation of several steroidogenic cytochrome P450 enzymes, their redox partner, and accessory proteins interacting with a range of biomimetic membranes. Paper 5 describes the results of a study dealing with the phenomenon of protein homodimerization in vivo and in vitro. Paper 6 describes the results of a study where the activities in biomimetic membrane of the two P450 aromatase enzymes were compared and the effect of the redox partner on each of the enzymes assessed. Papers 7 and 8 describe the results of a study on P450c17 enzyme system (including cytochrome P450 oxido-reductase (CPR), cytochrome b5 and a cytochrome b5 mutant). Paper 7 represents a PART 1 of this study in which the basic questions were considered, i.e. how these proteins bind to the biomimetic membrane individually and in sequence, and how their presence affects the properties of the membrane. Also, it describes the protein-protein interactions that occur during binding, highlighting their specificity. The activity of P450c17 was also tested, while the enzyme was bound to the biomimetic membrane, and positive results lead to a further exploration of this system. The results of this next stage of experiments are presented in Paper 8, representing a PART 2 of the study. Here, the effects of the CPR and the cytochrome b5 proteins on the activity of P450c17 were investigated, and the results highlight the role of protein-protein interactions mediated by the biomimetic membrane

Specific and Selective Peptide-Membrane Interactions Revealed Using Quartz Crystal Microbalance

AbstractThe skin secretions of Australian tree frogs are rich in peptides with potential antimicrobial activity. They interrupt bacterial cell membranes, although precisely how and whether all peptides have the same mechanism is not known. The interactions of three of these peptides—aurein 1.2, maculatin 1.1, and caerin 1.1 with supported phospholipid bilayers—are examined here using quartz crystal microbalance and atomic force microscopy. These approaches enabled us to reveal variations in material structure and density as a function of distance from the sensor surface when comparing mass sensorgrams over a range of harmonics of the natural resonance of the sensor crystal and hence obtain for the first time to our knowledge a mechanistic assessment of membrane disruption. We found that caerin inserted into the bilayer in a transmembrane manner, regardless of concentration and phospholipid composition consistent with a pore-forming mechanism. In contrast, maculatin and aurein interacted with membranes in a concentration-dependent manner. At low concentrations (<5μM), maculatin exhibited transmembrane incorporation whereas aurein was limited to surface association. Upon reaching a threshold value of concentration, both peptides lysed the membrane. In the case of maculatin, the lysis progressed in a slow, concentration-dependent manner, forming mixed micelles, as shown by atomic force microscopy imaging. Aurein-induced lysis proceeded to a sudden disruption, which is consistent with the “carpet” mechanism. Both maculatin and aurein exhibit specificity toward phospholipids and thus have potential as candidates as antimicrobial drugs

QCM-D fingerprinting of membrane-active peptides

The increasing prevalence of antibiotic-resistant bacteria is becoming a public health crisis. Antimicrobial peptides (AMPs) are a promising solution, because bacterial resistance is less likely. Quartz crystal microbalance with dissipation monitoring (QCM-D) is a versatile and valuable technique for investigation of these peptides. This article looks at the different approaches to the interpretation of QCM-D data, showing how to extract the maximum information from the data. Five AMPs of diverse charge, length and activity are used as case studies: caerin 1.1 wild-type, two caerin 1.1 mutants (Gly15Gly19-caerin 1.1 and Ala15Ala19-caerin 1.1), aurein 1.2 and oncocin. The interaction between the AMP and a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membrane is analysed inter alia using frequency-dissipation plots (∆f-∆D plots) to ascertain the mechanism of action of the AMP. The ∆f-∆D plot can then be used to provide a fingerprint for the AMP-membrane interaction. Building up a database of these fingerprints for all known AMPs will enable the relationship between AMP structure and membrane activity to be better understood, hopefully leading to the future development of antibiotics without bacterial resistance.George A. McCubbin, Slavica Praporski, Stefania Piantavigna, Daniel Knappe, Ralf Hoffmann, John H. Bowie, Frances Separovic, Lisandra L. Marti