Supramolecular arrangements of an organometallic forming nanostructured films

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Materials Research. 2014; 17(6): 1375-1383 © 2014 DOI: Supramolecular Arrangements of an Organometallic Forming Nanostructured Films S. A. Camachoa*, P. H. B. Aokia, F. F. de Assisb, A. M. Piresa, K. T. de Oliveirab, C. J. L. Constantinoa a Departamento de Física, Química e Biologia – DFQB, Faculdade de Ciências e Tecnologia, Univ Estadual Paulista – UNESP, CEP 19060-900, Presidente Prudente, SP, Brazil b Departamento de Química, Universidade Federal de São Carlos – UFSCar, Rodovia Washington Luís, km 235 – SP -310, CEP 13565-905, São Carlos, SP, Brazil Received: March 11, 2014; Revised: July 8, 2014 Organometallic materials have become subject of intensive research on distinct technological applications. The Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques have proven to be suitable to address challenges inherent to organic devices, in which the film properties can be tuned at molecular level. Here, we report on the supramolecular arrangement of zinc(II)-protoporphyrin(IX) dimethyl ester (ZnPPIX-DME) using the Langmuir, LB and LS techniques, leading to nanostructured films. The π-A isotherms showed that π-π stacking interaction among ZnPPIX-DME molecules takes place at the air/water interface, favoring the formation of Langmuir films closely packed. The controlled growth of the LB and LS films was monitored via UV-Vis absorption spectroscopy, with the thickness per monolayer within 1.3 and 1.7 nm. The homogeneous topography found at microscale is no longer preserved at nanoscale, which is found rougher according to AFM data. The FTIR indicated that the ZnPPIX-DME is isotropically arranged on both LB and LS films. Keywords: ZnPPIX-DME, Langmuir film, Langmuir-Blodgett (LB), Langmuir-Schaefer (LS) 1. Introduction Porphyrins are a widely investigated class of high conjugated heterocycles1 in which four pyrrole rings are linked to each other in cyclic form through meso-methine bridges. When these molecules contain metals linked to their core structure, they are called metalloporphyrins and form complexes such as heme and chlorophylls2. Porphyrins are versatile molecules which physicochemical properties are very sensitive to the modification of their electronic distribution on the pyrrole ring3. They have been frequently employed as vapor sensors once their optical spectra can be modified as a result of the interaction between the porphyrin ring and the vapor molecule4-9. Specifically, metalloporphyrins have been used as amine vapor sensors due to the specific affinity between the metallic atom and the amine moiety4. Other important characteristic of the porphyrins is the ability to transfer oxygen and electrons. This ability comes from their intense Soret and moderate Q bands allowing to collect visible light efficiently in the light-harvesting process10 and thus make them promising for use in solar energy conversion10-12 and in light harvesting13-15. Most applications involving porphyrins and their derivatives are related to devices such as catalysts16-18 and sensors19-24. Therefore, it is essential the improvement and the development of techniques to obtain porphyrin forming supramolecular structures25. In this sense, several kinds of techniques such as micelles26, vesicles27, Langmuir-Blodgett *e-mail: (LB) films28,29, Langmuir-Schaefer (LS) films3,4 and Layerby-Layer films30,31 have been applied and optimized. Among them, LB and LS techniques represent widely employed deposition methods to fabricate porphyrin thin films in a controlled way onto solid substrates25,32. The conventional LB and LS techniques allow a supramolecular arrangement that can influence the optical and electrical properties of a deposited film and, as a consequence, the variation of such parameters can be targeted according to desired application to the high-performance devices32. In the present study we fabricated and characterized Langmuir film (monolayer at air/ water interface), LB film (Langmuir film vertically transferred from air/water interface onto solid substrate) and LS film (Langmuir film horizontally transferred from air/water interface to solid substrate) of the zinc(II)-protoporphyrin (IX) dimethyl ester (ZnPPIX-DME). Protoporphyrins are a kind of porphyrins that have side chains like methyl, propionic acid and vinyl group33. The Langmuir film was studied via surface pressure vs. mean molecular area (π-A) isotherms and was applied such as investigation tool of the π-π stacking interaction. The Brewster Angle Microscopy (BAM) images were also used to the study of the π-A isotherm, allowing visualize at microscopic level, the aggregation state of the molecules in the monolayer. We have also demonstrated the possibility of growing LB and LS multilayer films containing ZnPPIX-DME. The growth of the films was monitored by 1376 Camacho et al. ultraviolet-visible absorption (UV-Vis) spectroscopy, while the morphology was investigated by micro-Raman and atomic force microscopy (AFM). The spatial distribution of the LB and LS films with micrometer scale resolution was performed using micro-Raman technique. At nanometer scale, AFM images were characterized via thickness, RMS roughness (RMS, root mean square) and average height (height difference between peaks and valleys). Finally, Fourier transform infrared (FTIR) absorption spectroscopy in reflection and transmission modes was applied to verify a possible anisotropy in terms of molecular organization of ZnPPIX-DME forming LB and LS films. 2. Experimental 2.1. Material The protoporphyrin dimethyl ester (PPIX) was synthesized from hematoporphyrin under acid catalyzed dehydration conditions and also acid catalyzed esterification, which details are described in 34,35. Thus, the zinc(II)protoporphyrin (IX) dimethyl ester (ZnPPIX-DME), which molecular structure is given in Figure 1, was prepared from PPIX by simple metalation using Zn(OAc)2 in CHCl3/ MeOH. This porphyrinoid was characterized using 1H-NMR and UV-Vis. The dichloromethane (Merck) solvent was HPLC grade. The ultrapure water (18.2 MΩ cm) was acquired from a Milli-Q water purification system (model Simplicity). 2.2. Langmuir, Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) films The ZnPPIX-DME Langmuir, LB and LS films were fabricated using a Langmuir trough KSV-NIMA model KN 2002. The Langmuir films were produced on water subphase by spreading 40 µL of a 0.50 mg/mL (0.77 mmol/L) ZnPPIX-DME solution dissolved in dichloromethane. Materials Research The Langmuir monolayers at the air/water interface were characterized by π-A isotherms at 23 °C using the Wilhelmy method with the plate surface placed perpendicular to the barriers. The monolayer was symmetrically compressed under a constant barrier speed at 10 mm/min with the subphase containing ultrapure water. In addition, Brewster angle microscopy (BAM) images were obtained in Langmuir films of ZnPPIX-DME using a KSV micro-BAM microscope. The BAM images were collected for different areas and pressures during the compression of the film at the air/water interface. LB and LS films were obtained by transferring the ZnPPIX-DME Langmuir monolayers from the air/water interface onto different solid substrates depending on the characterization technique to be applied. The surface pressure was kept constant at 30 mN/m and the barrier speed at 10 mm/min (symmetrical compression). LB films were deposited by emerging the substrate vertically with upstroke speeds from 0.2 to 1.0 mm/min. The deeper speed was varied within this interval during the deposition to keep the transfer ratio (TR) close to 1, leading to Z-type LB films. For the LS films, the deposition was carried out approaching manually and horizontally the substrate to the air/water interface. 2.3. Film characterization The ZnPPIX-DME solution in dichloromethane (2.5 × 10 –5 mol/L) and the LB and LS film growth were monitored via UV–Vis absorption spectroscopy using a Varian spectrophotometer, model Cary 50, from 190 to 1100 nm. For UV-Vis absorption spectroscopy characterization, LB and LS films containing up to 9 layers were deposited onto quartz substrate. Raman analysis and optical microscopy were carried out using a spectrograph micro-Raman Renishaw model in-Via equipped with a Leica microscope, which 50x objective lens allows collecting the spectra with a spatial resolution of ca. 1 µm2, a CCD detector, laser lines at 514.5 and 633 nm, 1800 groove/mm gratings Figure 1. (a) ZnPPIX-DME π-A isotherm recorded for the ultrapure water subphase at room temperature (23 °C). The inset A is a scheme illustrating the ZnPPIX-DME Langmuir film at the air/water interface and inset B the π-π interaction between protoporphyrin rings. The approximate dimension of the ZnPPIX-DME molecule is given as a detail. (b) ZnPPIX-DME π-A isotherms recorded for different compression speeds. The inset C displays the dependence of the corresponding molecular area at 30 mN/m on compression speed (the bars correspond to the interval found for the three isotherms recorded for each compression speed). 2014; 17(6) Supramolecular Arrangements of an Organometallic Forming Nanostructured Films with additional edge filters, and a computer-controlled three-axis-encoded (XYZ) motorized stage to take Raman images with a minimum step of 0.1 µm. The AFM images for the LB and LS films were obtained using a Nanosurf instrument model easyScan 2, with a tip of silicon nitride, in the tapping mode. All images were collected with high resolution (512 lines per scan) at a scan rate of 0.5 Hz. The images were characterized by using the software Gwyddion 2.19 to analyze the average height and RMS roughness of the topographic images. The FTIR measurements were taken using a spectrometer Bruker model Tensor 27 with spectral resolution of 4 cm–1 and 128 scans, using a DTGS detector. The spectra in reflection mode were obtained with an incident angle of radiation of 80° using a Bruker accessory A118. LB films with 30 layers were deposited onto Ge substrate and 50 layers on Au mirror for FTIR measurements in transmission and reflection modes, respectively. For LS films 60 layers were deposited onto Ge substrate and Au mirror for the same FTIR measurements. 3. Results and Discussion 3.1. ZnPPIX-DME Langmuir films Figure 1 displays the π-A isotherms of ZnPPIX-DME Langmuir films. The well-defined pattern of the gas, liquid and solid-like phases are not observed during compression of the monolayer. When approaching the solid phase, the π-A isotherm displays high slope toward 35 mN/m. From then on, a phase transition is seen and a long process with a less marked slope takes place. Borovkov et al.9 and Valli et al.6 also observed the same phase transition working with Langmuir films of bis(zinc porphyrin) and zinc porphyrin, respectively. Borovkov et al.9 attributed the existence of these two phases to the increase in size of three-dimensional aggregates. Nevertheless, there are not significant changes in the surface pressure that indicate the monolayer collapse. According to Bergeron et al.36 the rigidity of such films turns it difficult to determine where exactly the collapse begins. 1377 The occupied area per ZnPPIX-DME molecules is estimated to be ca. 58 Å2 by extrapolating the linear region of the isotherm, before the phase transition, to zero pressure (Figure 1a). Considering the approximate dimensions of the ZnPPIX-DME molecules, the ZnPPIX-DME molecular area into Langmuir films is smaller than the molecular area of the protoporphyrin macrocycle lying flat on the air/water interface (145 Å2). On the other hand, the occupied area (58 Å2) determined via π-A isotherms is comparable to the calculated value (5 × 12 = 60 Å2)[36] for the ZnPPIX-DME with the ester groups facing the air/water interface. A similar molecular arrangement was found by Jin et al.37 and Li et al.28 for Langmuir films made of iron(III) and zinc(II) protoporphyrins, respectively. This possible molecular arrangement might be related to a strong attractive π-π interaction between protoporphyrin rings leading to the molecular aggregation at the air/water interface. Indeed, the presence of the ester moieties facing the water subphase favors the formation of Langmuir films closely packed by the strong π-π stacking interaction28,37, as depicted by insets A and B in Figure 1a. Figure 1b displays the effect of the compression speed on the packing of the Langmuir film. The dependence of the corresponding molecular area at 30 mN/m on compression speed is shown in inset C. The molecular area increases up to a plateau with the increasing of compression speed. The latter is related to the time the ZnPPIX-DME molecules have to rearrange and pack on the air/water interface. The slower the compression speed the smaller the molecular area due to the formation of Langmuir films closely packed by the strong π-π stacking interaction. Figure 2a shows different cycles of compression and expansion of ZnPPIX-DME Langmuir films. A small hysteresis is seen after the first cycle, which indicates the formation of molecular aggregates during the first compression. The subsequent cycles reproduce each other indicating that the aggregates formed as a result of the π-π stacking interaction are stable, i.e., they are formed during the first compression and are kept as it is. The BAM images recorded for different compression stages are shown Figure 2. (a) ZnPPIX-DME π-A isotherms obtained by four compression-expansion consecutive cycles. (b) The BAM images recorded for different compression stages of the film. 1378 Camacho et al. in Figure 2b. Significant domains are found even before starting the monolayer compression (π = 0 mN/m), which is an evidence of π-π interactions leading to ZnPPIXDME aggregation. The presence of large domains is still predominant into the gas-phase reached at low surface pressures (π = 2 mN/m) by compressing the monolayer. Borovkov et al.9 also observed the co-existence of gas and condensed domains in Langmuir films of an bis(zinc porphyrin) and also attributed this event to the presence of aggregates on the water surface. The increase of surface pressure toward the liquid-phase (π = 10 mN/m) and condensed-phase (π = 30 mN/m) increases the Langmuir monolayer uniformity and large domains are no longer observed. This is the stage (named solid phase) in which the Langmuir monolayer is transferred to solid substrates forming either LB or LS films. By releasing the surface pressure of the Langmuir film (expansion), large domains are once more observed, equally to the observed prior compression. The latter is in agreement to the aggregation stability found by the hysteresis in the π-A isotherms. 3.2. Growth of ZnPPIX-DME forming LB and LS films The growth of the LB and LS films was monitored using UV-Vis absorption spectroscopy. Figures 3a and 3b present the UV-Vis spectra for both LB and LS films, respectively, recorded every 2 layers up to 9 layers. The ZnPPIX-DME solution spectrum is given as reference and scaled to fit the plot. The ZnPPIX-DME molecules in the solution exhibit three main absorption bands with maxima at 409, 539 and 577 nm, assigned to one Soret band and two Q-bands36,38-40, respectively. The insets in Figures 3a and 3b show the absorbance at 406 and 404 nm for the different numbers of deposited layers in the LB and LS films, respectively. The linear growth of absorbance indicates that similar amounts of ZnPPIXDME are transferred per deposited monolayer, revealing a controlled growth of both LB and LS films. Besides, Materials Research in terms of absorbance values, considering that for LB films the monolayers are transferred onto both sides of the substrate while for LS films the monolayers are transferred onto only one side of the substrate, then approximately the same amount of ZnPPIX-DME is deposited per monolayer for both LB and LS films. 3.3. Morphology at micro and nanometer scales of ZnPPIX-DME forming LB and LS films The spatial distribution of the ZnPPIX-DME in the LB and LS films at micrometer scale resolution was performed using micro-Raman technique, combining morphological and chemical information with an optical microscope coupled to a Raman spectrograph. Figures 4a and 4b show the Raman spectra and optical images taken from both ZnPPIX-DME LB and LS films, respectively. Both optical images revealed a highly homogeneous film surface at the microscale, with absence of aggregates. Besides, different spectra recorded from distinct spots present high similarity each other in terms of band frequencies (Figure 4a), indicating that ZnPPIX-DME molecules are homogeneously distributed throughout the LB and LS films. Slightly differences are found considering the band relative intensities of the spectra collected for LB and LS films. The BAM images (Figure 2b) suggest that Langmuir films are formed by domains that might contain different structuration of ZnPPIX-DME molecules. In micro-Raman experiments, the probed area of the laser is ca. 1µm 2. Therefore, those the differences in Raman spectra might be related to different spots probed by the laser, containing domains with distinct structuration of ZnPPIX-DME molecules. This effect is not comparable to techniques such as FTIR and UV-Vis, which probed area of the radiation beam is about mm2. The spectra collected in these cases are an average of the combined response of different domains, leading to smaller variation. Figures 5a and 5b show AFM images (2 and 3 dimensions) for ZnPPIX-DME LB and LS films, respectively. The AFM Figure 3. UV-Vis absorption spectra for (a) LB and (b) LS films containing different numbers of ZnPPIX-DME monolayers transferred onto quartz with the ultrapure water subphase at room temperature (23 °C). The films were grown in a constant surface pressure at 30 mN/m. The insets show the absorbance at the Soret band vs. the number of deposited monolayers. The active. HIV-infected patients displayed a redistribution of body fat as the percentage of fat on the limb were lower and the percentage of fat in the trunk was higher compared to control subjects. The patients also had disturbances in their lipid metabolism as fasting triglycerides and total-cholesterol levels were higher, and HDL-cholesterol level was lower. In addition, compared to controls, the HIV-infected patients were characterized by peripheral insulin resistance as whole-body insulin-stimulated glucose uptake (Rd) and incremental glucose uptake (Rd basal – Rd clamp) were decreased. Furthermore, the HIV subjects had higher basal endogenous glucose production, lower insulin-mediated suppression of endogenous glucose production (Ra), but no difference in the incremental suppression of endogenous glucose production during the clamp (Ra basal – Ra clamp) as compared to control subjects. Plasma FGF-21 and FGF-21mRNA in muscle Plasma FGF-21 was elevated in the HIV-group compared to healthy controls (70.4656.8 pg/ml vs 109.1671.8 pg/ml, respectively) (P = 0.04) (Figure 1A). FGF-21 mRNA expression in skeletal muscle was increased 8fold in patients with HIV relative to healthy individuals (P,0.0001, parametric statistics, and p = 0.0002 for non-para- metric statistics) (Figure 1B). The association between plasma FGF-21 and muscle FGF-21 did not reach statistical significance (r = 0.32; p = 0.056). Relationships between FGF-21 mRNA, plasma FGF-21 and insulin resistance Muscle FGF-21 mRNA correlated positively to all markers of insulin resistance: fasting insulin (r = 0.57, p = 0.0008), homeostasis model assessment (HOMA) score (r = 0.55, p = 0.001), and insulinAUC (r = 0.38, p = 0.02) (Fig. 1 C–F). To test whether the association between insulin and FGF-21 mRNA in muscle reflect an association with peripheral or hepatic insulin resistance, we performed a euglycemic-hyperinsulinemic clamp with stable isotopes. We found that muscle FGF-21 mRNA was negatively associated with the insulin-mediated glucose-uptake (Figure 1G), but not with hepatic insulin resistance (data not shown). We did not find any association between plasma FGF-21 and parameters of insulin resistance (fasting insulin, plasma glucose, HOMA-IR, glucose AUC, Insulin AUC, Ra or Rd). However, when investigating by group, plasma FGF-21 correlated positive with insulin stimulated glucose-uptake in healthy subjects but not in the HIV patients (r = 0.51, p = 0.049) (data not shown). Previous studies have demonstrated that insulin resistance in patients with HIV-LD are associated with decreased insulinstimulated glycogen synthase (GS) activity [24]. Therefore, we measured GS activity. The GS fractional velocity of % total GS activity was lower in HIV patients compared with healthy controls (2861.3; 3561.6, respectively) in the basal stage. GS fractional velocity is known to correlate positively with the glucose Rd [25]. As high FGF-21 mRNA in muscle is associated with low rate of disappearance of glucose, this could be linked to low GS fractional velocity in muscle. In accordance with this hypothesis, we found that high levels of FGF-21 mRNA in muscle were associated with decreased GS fractional velocity in muscle (Fig. 1H). Relationships between muscle FGF-21 mRNA, and fat distribution and lipids We found a strong negative association between muscle FGF-21 mRNA and the amount of subcutaneous fat (limb fat mass) (r = 20.46; p = 0.0038) and positive association with trunk-limbfat-ratio (r = 0.51; p = 0.001) and triglycerides (r = 0.56; p = 0.0003). FGF-21 mRNA was not associated with total fat mass or total trunk fat (data not shown). Discussion The novelty and the major findings of our study is that we demonstrate for the first time that FGF-21 mRNA expression is increased in skeletal muscle in patients with HIV-LD compared to healthy age-matched men and that muscle FGF-21 mRNA correlates negatively with the rate of insulin-stimulated glucose disappearance (primarily reflecting muscle). Furthermore, increased FGF-21 mRNA expression in muscle is associated with decreased limb fat mass, increased waist-to-hip ratio and increased triglycerides. Only three studies are published on expression of FGF-21 in muscle in humans [10,12,26] and very little is known about the function of muscle FGF-21. Our result is in agreement with a previous study, in which FGF-21 mRNA was found to be increased in muscle from subjects with type 2 diabetes and the expression was increased by hyperinsulinemia [10]. However, this study did not distinguish between hepatic and peripheral insulin sensitivity as we do in the present study. Vienberg et al. [12] also PLOS ONE | 3 March 2013 | Volume 8 | Issue 3 | e55632 Muscle FGF-21,Insulin Resistance and Lipodystrophy Table 1. Baseline characteristics of patients and healthy controls. Age (years) Duration of HIV infection (years) Duration of antiretroviral therapy (years) CD4+ cell (cells/ml) LogHIV-RNA (copies/ml) Antiretroviral use NNRTI-based HAART, PI-based HAART, NNRTI-,PI-based HAART regime, No. Current Thymidine-NRTI use, No. (%) Current PI use, No. (%) Current NNRTI use, No. (%) Physical activity parameters VO2max (LO2/min) Body composition Body-mass index (kg/m2) Weight (kg) Waist (cm) Waist-to.hip ratio Fat mass (kg) Trunk fat mass (kg) Trunk fat percentage (%) Limb fat mass (kg) Limb fat percentage (%) Trunk-to-limb fat ratio Lean mass (kg) Metabolic parameters Total-cholesterol (mmol/L) HDL-C (mmol/L) LDL-C (mmol/L) Triglycerides (mmol/L) Glucose (mmol/L) Insulin (pmol/L) HOMA-IR Insulin sensitivity Rate of appearance (mmol glucose/kg/min) Basal Clamp Delta{ Rate of disappearance (mmol glucose/kg/min) Basal Clamp Delta{ Glucose tolerance Glucose area under the curve (mmol/Lmin) Insulin area under the curve (pmol/Lmin) HIV patients (n = 23) 47.9 (9.5) 15.6 (9.6) 10.3 (4.3) 558 (208) 1.33 (0.12) 12/14/2 11 (47.8) 13 (56.7) 11 (47.8) 2.3 (0.5) 23.7 (2.9) 73.6 (11.2) 93.6 (6.4) 1.01 (0.04) 13.8 (5.3) 9.8 (3.9) 71.2 (6.2) **** 3.5 (1.6)**** 25.1 (6.1) **** 3.09 (1.17)* 57.0 (6.8) 5.5 (0.9)** 1.23 (0.52)* 3.7 (0.9) 2.55(1.43)**** 5.4 (0.6) 52 (25)**** 2.2 (1.4)**** 14.2 (0.49)*** 6.4 (1.8)** 7.8 (2.1) 14.2 (0.49)*** 40.2 (9.9)** 26.02 (10.1)** 826 (200)* 52360 (31017)** Healthy controls (n = 15) 47.5 (6.1) 2.5 (0.6) 23.7 (1.9) 76.9 (7.4) 90 (5.7) 0.94 (0.03) 15.7 (4.4) 8.9 (3.0) 56.1(5.2) 6.2 (1.5) 40.2 (4.9) 1.4 (0.29) 58.2 (5.2) 4.63 (0.64) 1.51 (0.32) 3.3 (0.6) 0.76 (0.24) 5.2 (0.3) 25 (8.9) 0.99 (0.37) 11.8 (2.0) 4.0 (2.5) 7.8 (1.9) 11.8 (2.0) 48.6 (8.4) 36.81 (7.14) 670 (126) 23505 (10598) Data are presented as mean (SD). {Delta, differences between clamp and basal values. HAART, highly active antiretroviral therapy; PI, protease inhibitor; NRTI, nucleoside reverse transcriptase inhibitor; NNRTI, non- nucleoside reverse transcriptase inhibitor. HOMA-IR, homeostatic model assessment for insulin resistance, Rate of appearance and disappearance, Rate of appearance and disappearance of glucose during a euglycemic-hyperinsulinemic clamp performed in both HIV patients and healthy controls. *P,0.05; **P,0.01; ***P,0.001, ****P,0.0001 by t-test. doi:10.1371/journal.pone.0055632.t001 PLOS ONE | 4 March 2013 | Volume 8 | Issue 3 | e55632 Muscle FGF-21,Insulin Resistance and Lipodystrophy Figure 1. FGF-21 mRNA are increased in muscle from subjects with HIV-lipodystrophy and correlates to several measurement of insulin resistance. (A) Fasting plasma levels of fibroblast growth factor (FGF) 21 are increased 2-fold in HIV subjects with lipodystrophy compared to healthy men; (B) mRNA expression of FGF-21 are increased 8-fold in muscle biopsies from HIV subjects with lipodystrophy compared to healthy men; (C–F) Plots of FGF-21 mRNA in muscle versus several measurements of insulin resistance: FGF-21 mRNA in muscle are positively correlated to fasting insulin (C), HOMA-IR (D), Area under the curve for insulin during an oral glucose tolerance test (E), Area under the curve for C-peptide during Nan oral glucose tolerance test (F), and negatively correlated to the incremental rate of disappearance of glucose (G), and fractionel velocity of glycogen synthesis (H) in healthy (e) and HIV subjects with lipodystrophy ( ). In the dot plots data for each subjects are given and the line represent means. * P,0.05 and ***P,0.001 for healthy vs HIV-lipodystrophy patients. For plots, linear regression lines, correlations coefficient, and significance levels are given for all subjects. doi:10.1371/journal.pone.0055632.g001 PLOS ONE | 5 March 2013 | Volume 8 | Issue 3 | e55632 Muscle FGF-21,Insulin Resistance and Lipodystrophy find that FGF-21 mRNA was expressed in muscle, but they find no activation of muscle FGF-21 mRNA by a short term high fat overfeeding. In the study by Mashili et al. [26], FGF-21 mRNA was expressed in skeletal muscle, but in the aquatic environment for long-term survival and for transmission to arthropod and mammalian hosts. References 1. Ray K, Marteyn B, Sansonetti PJ, Tang CM. Life on the inside: the intracellular lifestyle of cytosolic bacteria. Nature reviews. 2009; 7(5):333–40. doi: 10.1038/nrmicro2112 PMID: 19369949 2. Kingry LC, Petersen JM. Comparative review of Francisella tularensis and Francisella novicida. Frontiers in cellular and infection microbiology. 2014; 4:35. doi: 10.3389/fcimb.2014.00035 PMID: 24660164 3. 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