Structural Diversity of Native Major Ampullate, Minor Ampullate, Cylindriform, and Flagelliform Silk Proteins in Solution.

The foundations of silk spinning, the structure, storage, and activation of silk proteins, remain highly debated. By combining solution small-angle neutron and X-ray scattering (SANS and SAXS) alongside circular dichroism (CD), we reveal a shape anisotropy of the four principal native spider silk feedstocks from Nephila edulis. We show that these proteins behave in solution like elongated semiflexible polymers with locally rigid sections. We demonstrated that minor ampullate and cylindriform proteins adopt a monomeric conformation, while major ampullate and flagelliform proteins have a preference for dimerization. From an evolutionary perspective, we propose that such dimerization arose to help the processing of disordered silk proteins. Collectively, our results provide insights into the molecular-scale processing of silk, uncovering a degree of evolutionary convergence in protein structures and chemistry that supports the macroscale micellar/pseudo liquid crystalline spinning mechanisms proposed by the community.

Dry-Spun Silk Produces Native-Like Fibroin Solutions.

Silk's outstanding mechanical properties and energy efficient solidification mechanisms provide inspiration for biomaterial self-assembly as well as offering a diverse platform of materials suitable for many biotechnology applications. Experiments now reveal that the mulberry silkworm Bombyx mori secretes its silk in a practically "unspun" state that retains much of the solvent water and exhibits a surprisingly low degree of molecular order (ß-sheet crystallinity) compared to the state found in a fully formed and matured fiber. These new observations challenge the general understanding of silk spinning and in particular the role of the spinning duct for structure development. Building on this discovery we report that silk spun in low humidity appears to arrest a molecular annealing process crucial for ß-sheet formation. This, in turn, has significant positive implications, enabling the production of a high fidelity reconstituted silk fibroin with properties akin to the gold standard of unspun native silk.

Identification and classification of silks using infrared spectroscopy.

Lepidopteran silks number in the thousands and display a vast diversity of structures, properties and industrial potential. To map this remarkable biochemical diversity, we present an identification and screening method based on the infrared spectra of native silk feedstock and cocoons. Multivariate analysis of over 1214 infrared spectra obtained from 35 species allowed us to group silks into distinct hierarchies and a classification that agrees well with current phylogenetic data and taxonomies. This approach also provides information on the relative content of sericin, calcium oxalate, phenolic compounds, poly-alanine and poly(alanine-glycine) ß-sheets. It emerged that the domesticated mulberry silkmoth Bombyx mori represents an outlier compared with other silkmoth taxa in terms of spectral properties. Interestingly, Epiphora bauhiniae was found to contain the highest amount of ß-sheets reported to date for any wild silkmoth. We conclude that our approach provides a new route to determine cocoon chemical composition and in turn a novel, biological as well as material, classification of silks.

Cleaning-in-place of immunoaffinity resins monitored by in situ ATR-FTIR spectroscopy.

In the next 10 years, the pharmaceutical industry anticipates that revenue from biotherapeutics will overtake those generated from small drug molecules. Despite effectively treating a range of chronic and life-threatening diseases, the high cost of biotherapeutics limits their use. For biotherapeutic monoclonal antibodies (mAbs), an important production cost is the affinity resin used for protein capture. Cleaning-in-place (CIP) protocols aim to optimise the lifespan of the resin by slowing binding capacity decay. Binding assays can determine resin capacity from the mobile phase, but do not reveal the underlying causes of Protein A ligand degradation. The focus needs to be on the stationary phase to examine the effect of CIP on the resin. To directly determine both the local Protein A ligand concentration and conformation on two Protein A resins, we developed a method based on attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. ATR-FTIR spectroscopic imaging revealed that applying a carefully controlled load to agarose beads produces an even and reproducible contact with the internal reflection element. This allowed detection and quantification of the binding capacity of the stationary phase. ATR-FTIR spectroscopy also showed that Protein A proteolysis does not seem to occur under typical CIP conditions (below 1 M NaOH). However, our data revealed that concentrations of NaOH above 0.1 M cause significant changes in Protein A conformation. The addition of >0.4 M trehalose during CIP significantly reduced NaOH-induced ligand unfolding observed for one of the two Protein A resins tested. Such insights could help to optimise CIP protocols in order to extend resin lifetime and reduce mAb production costs.

High-throughput thermal stability analysis of a monoclonal antibody by attenuated total reflection FT-IR spectroscopic imaging.

The use of biotherapeutics, such as monoclonal antibodies, has markedly increased in recent years. It is thus essential that biotherapeutic production pipelines are as efficient as possible. For the production process, one of the major concerns is the propensity of a biotherapeutic antibody to aggregate. In addition to reducing bioactive material recovery, protein aggregation can have major effects on drug potency and cause highly undesirable immunological effects. It is thus essential to identify processing conditions which maximize recovery while avoiding aggregation. Heat resistance is a proxy for long-term aggregation propensity. Thermal stability assays are routinely performed using various spectroscopic and scattering detection methods. Here, we evaluated the potential of macro attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopic imaging as a novel method for the high-throughput thermal stability assay of a monoclonal antibody. This chemically specific visualization method has the distinct advantage of being able to discriminate between monomeric and aggregated protein. Attenuated total reflection is particularly suitable for selectively probing the bottom of vessels, where precipitated aggregates accumulate. With focal plane array detection, we tested 12 different buffer conditions simultaneously to assess the effect of pH and ionic strength on protein thermal stability. Applying the Finke model to our imaging kinetics allowed us to determine the rate constants of nucleation and autocatalytic growth. This analysis demonstrated the greater stability of our immunoglobulin at higher pH and moderate ionic strength, revealing the key role of electrostatic interactions. The high-throughput approach presented here has significant potential for analyzing the stability of biotherapeutics as well as any other biological molecules prone to aggregation.

A poisonous surprise under the coat of the African crested rat.

Plant toxins are sequestered by many animals and the toxicity is frequently advertised by aposematic displays to deter potential predators. Such 'unpalatability by appropriation' is common in many invertebrate groups and also found in a few vertebrate groups. However, potentially lethal toxicity by acquisition has so far never been reported for a placental mammal. Here, we describe complex morphological structures and behaviours whereby the African crested rat, Lophiomys imhausi, acquires, dispenses and advertises deterrent toxin. Roots and bark of Acokanthera schimperi (Apocynaceae) trees are gnawed, masticated and slavered onto highly specialized hairs that wick up the compound, to be delivered whenever the animal is bitten or mouthed by a predator. The poison is a cardenolide, closely resembling ouabain, one of the active components in a traditional African arrow poison long celebrated for its power to kill elephants.

Hepatitis C recurrence after liver transplantation: has the human leukocyte antigen mismatching at individual loci a role?

BACKGROUND AND AIM: The objective of this 11-year cohort retrospective study conducted in adult patients with chronic hepatitis C virus (HCV) who underwent liver transplantation (LT) was to identify whether human leukocyte antigen (HLA) mismatching is associated with the recurrence of HCV and with the time to recurrence of HCV. METHODS: Among the 181 patients (74% men; mean age: 54 years, range 25-71) who underwent a LT between 1995 and 2006 in the study center, 163 had relevant data in their medical chart documenting HCV recurrence, and 107 (65.64%) reported a histological evidence of HCV recurrence. RESULTS: Survival was 78% at 5 years. There was no significant relationship between the total score of HLA-mismatches and the recurrence of HCV. Similarly, there was no significant relationship between the total score of HLA mismatches and the time to recurrence of HCV. For the analyses at each individual locus, a significant relationship between the individual scores of HLA-mismatches and the recurrence of HCV were observed. Out of the 40 patients who experienced a rejection, the rate of recurrence was not different according to the severity of the rejection (75% mild, 64% moderate and 64% for severe rejection). CONCLUSIONS: In conclusion, this large study did not demonstrate any relationship between the total score of HLA mismatches and HCV-recurrence. Contrarily a significant relationship between the individual scores of HLA mismatches (HLA-A3, HLA-B35, HLA-DR3, HLA-DR7, HLA-DQ2, HLA-DQ2-0) and the recurrence of HCV were observed.

Rheo-attenuated total reflectance infrared spectroscopy: a new tool to study biopolymers.

Whilst rheology is the reference technique to study the mechanical properties of unspun silk, we know little of the structure and the dynamics that generate them. By coupling infrared spectroscopy and shearing forces to study silk fibroin conversion, we are introducing a novel tool to address this gap in our knowledge. Here the silk conversion process has been studied dynamically using polarized attenuated total reflectance Fourier transform infrared spectroscopy whilst applying shear, thus revealing silk protein conformation and molecular orientation in situ. Our results show that the silk conversion process starts with a pre-alignment of the proteins followed by a rapid growth of the ß-sheet formation and then a subsequent deceleration of the growth. We propose that this tool will provide further insight into not only silk but any biopolymer solution, opening a new window into biological materials.

Robotic liver resection as a bridge to liver transplantation.

BACKGROUND: The surgical robotic system is superior to traditional laparoscopy in regards to 3-dimensional images and better instrumentation. Robotic surgery for hepatic resection has not yet been extensively reported. The aim of this article is to report the first known case of liver resection with the use of a robot in France. METHODS: A 61-year-old male with hepatitis C liver cirrhosis and hepatocellular carcinoma was referred for surgical treatment. Preoperative clinical evaluation and laboratory data disclosed a Child-Pugh class A5 patient. Magnetic resonance imaging showed a 3.4-cm tumor in segment III. Liver size was normal, and there were not signs of portal hypertension. Five trocars were used. RESULTS: Liver transection was achieved with Harmonic scalpel and bipolar forceps without pedicle clamping. Hemostasis of raw surface areas was accomplished with interrupted stitches. Operative time was 180 minutes. Blood loss was minimal, and the patient did not receive transfusion. The recovery was uneventful, and the patient was discharged on the fifth postoperative day without ascites formation. CONCLUSION: The robotic approach may enable liver resection in patients with cirrhosis. The da Vinci robotic system allowed for technical refinements of laparoscopic liver resection due to 3-dimensional visualization of the operative field and instruments with wrist-type end-effectors.

Study of the interaction of lactoferricin B with phospholipid monolayers and bilayers.

Bovine lactoferricin (LfcinB) is an antimicrobial peptide obtained from the pepsin cleavage of lactoferrin. The activity of LfcinB has been extensively studied on diverse pathogens, but its mechanism of action still has to be elucidated. Because of its nonspecificity, its mode of action is assumed to be related to interactions with membranes. In this study, the interaction of LfcinB with a negatively charged monolayer of dipalmitoylphosphatidylglycerol has been investigated as a function of the surface pressure of the lipid film using in situ Brewster angle and polarization modulation infrared reflection absorption spectroscopy and on transferred monolayers by atomic force microscopy and polarized attenuated total reflection infrared spectroscopy. The data show clearly that LfcinB forms stable films at the air-water interface. They also reveal that the interaction of LfcinB with the lipid monolayer is modulated by the surface pressure. At low surface pressure, LfcinB inserts within the lipid film with its long molecular axis oriented mainly parallel to the acyl chains, while at high surface pressure, LfcinB is adsorbed under the lipid film, the hairpin being preferentially aligned parallel to the plane of the interface. The threshold for which the behavior changes is 20 mN/m. At this critical surface pressure, LfcinB interacts with the monolayer to form discoidal lipid-peptide assemblies. This structure may actually represent the mechanism of action of this peptide. The results obtained on monolayers are correlated by fluorescent probe release measurements of dye-containing vesicles made of lipids in different phases and support the important role of the lipid fluidity and packing on the activity of LfcinB.

Four hundred and twenty-three consecutive adults piggy-back liver transplantations with the three suprahepatic veins: was the portal systemic shunt required?

BACKGROUND AND AIMS: The aim of this study is to analyze a single-center experience in orthotopic liver transplantation with the piggy-back technique (PB) realized with a cuff of three veins without temporary portacaval shunt. Outcome parameters were graft and patient survival and the surgical complications. METHODS: The records of 423 liver transplantation in 396 adult recipients were reviewed. PB was performed in all cases also in patients with transjugular intrahepatic portosystemic shunts and redo transplants without temporary portacaval shunt. No hemodynamic instability was observed during venous reconstruction. RESULTS: Operation time, cold ischemia time and anhepatic phase were, respectively, 316, 606 and 82 min, respectively. The mean intraoperative transfusion of packed red blood cells was 3.2 (range 1-48). Surgical complications were observed in 25% of the orthotopic liver transplantation and 2% of these was related to caval anastomosis. No case of caval thrombosis was observed; a stenosis was noted in seven patients, always treated with an endovascular approach. A postoperative ascites was observed in seven cases. Retransplantation was required in 6.3% patients. Overall in-hospital mortality was 5.3%, but no patient died through technical problems or complications related to PB procedure. One-, 3- and 5-year grafts and patients were 94%, 83% and 75%, and 92%, 86% and 79%, respectively. CONCLUSION: This experience indicates that our approach is feasible with a low specific risk and can be performed without portacaval shunt, with minimal outflow venous complications.

Reye syndrome and liver transplantation.

Reye syndrome is a rare, but severe and often fatal disease. The etiology of the classical Reye syndrome is unknown, but it is typically preceded by a viral infection with a free interval of three to five days. The main physiopathological hypothesis is a mitochondrial metabolism insult causing acute liver failure and encephalopathy. Survivors present serious neurological sequelae. The treatment of Reye syndrome is usually medical with intensive care management. Herein, we present the clinical case of a six-month-old baby diagnosed with Reye syndrome with a fulminant hepatitis, who was successfully liver transplanted with an auxiliary partial orthotopic liver transplantation.

Passenger lymphocyte syndrome and liver transplantation.

The authors reviewed the passenger lymphocyte syndrome (PLS) that has appeared after transplantation. The definition, mechanism, serological, clinical features, and treatment for PLS after solid organ transplantation, especially liver transplantation, are described. The PLS refers to the clinical phenomenon of alloimmune hemolysis resulting from the adoptive transfer of viable lymphocytes from donor during solid organ or hematopoietic stem cell transplant. Sometimes, it is very severe and may cause "unexplained" hemolysis during the postoperative period. The authors reviewed literature about the PLS in liver transplantation.

Attenuated total reflection infrared spectroscopy: an efficient technique to quantitatively determine the orientation and conformation of proteins in single silk fibers.

Polarized attenuated total reflection (ATR) infrared spectroscopy is an efficient technique to determine the orientation and conformation of a large variety of samples, but it is more difficult to apply to very small specimens such as silk fibers. The Golden Gate single-reflection ATR accessory that uses diamond as an ATR element and a focalized beam turns out to be highly efficient to study quantitatively the orientation and conformation of a single silk fibroin filament of the silkworm Bombyx mori that is about 10 mum in diameter. For orientation measurements, rotating the sample instead of the electric field greatly simplifies the theoretical analysis and keeps the penetration depth of the infrared radiation constant. A sample holder that can be fitted on the ATR accessory has thus been developed to allow accurate rotation of the sample and to obtain spectra with a low, non-damaging, and reproducible pressure on the fiber. To validate the method, spectra have been recorded as a function of the angle theta between the fiber axis and the polarization of the incident radiation. The data have been fitted following the cosine square dependency of the absorbance with respect to the angle theta. The procedure has been applied to the spectral components of the amide I bands, as determined from spectral decomposition. Multiple angle measurements turn out to be quite useful to correct systematic angle errors and validate the accuracy of the curve-fitting parameters of the band decomposition. By using the calculated dichroic ratio, a parameter of -0.46+/-0.01 has been calculated for the antiparallel beta-sheets and -0.04+/-0.02 for the remaining structures. From the orientation-insensitive spectrum A0, the amount of beta-sheets has been estimated to 49+/-3%. The results obtained from only two measurements with the electric field of the incident radiation parallel and perpendicular to the fiber axis has demonstrated that ATR spectroscopy can be used routinely in quantitative studies of the molecular orientation and conformation of macromolecules.

Significance of the depth of portal vein wall invasion after curative resection for pancreatic adenocarcinoma.

HYPOTHESIS: The depth of portal vein (PV) wall invasion is a prognostic factor for survival after curative pancreatic resection for pancreatic ductal adenocarcinoma. DESIGN: Retrospective clinical study. SETTING: Department of digestive surgery and transplantation. PATIENTS: From January 1, 1990, through December 31, 2002, 121 patients underwent a curative pancreatic resection for ductal adenocarcinoma of the pancreas. Among these, 37 pancreatic resections combined with PV resection were performed. MAIN OUTCOME MEASURES: Prognostic factors for survival and predictive factors for the depth of PV wall invasion. RESULTS: The morbidity and mortality rates did not differ between patients undergoing or not undergoing PV resection (32.4% and 2.7% [1/37], respectively, vs 38.1% and 2.4% [2/84], respectively). The 3-year survival rate after curative pancreatic resection was significantly associated with the depth of PV wall invasion. Indeed, the 3-year overall survival rate was similar for patients with no PV invasion and those with superficial invasion into the tunica adventitia (40.0% vs 32.9%, respectively; P = .85). Deeper PV wall invasion into the tunica media or the tunica intima was associated with a poorer 1-year survival rate similar to that of patients undergoing noncurative resection (21.5% vs 34.4%, respectively; P = .53). Multivariate analysis showed that the depth of PV wall invasion, number of involved lymph nodes, and volume of blood transfusion were independent factors of overall and disease-free survival. Tumor size of 45 mm or more (evaluated by computed tomography) and angiographic type C or D on a portogram were significantly correlated with the depth of PV wall invasion. Patients presenting with both factors simultaneously had poor survival. CONCLUSIONS: The depth of PV wall invasion significantly alters survival after curative pancreatic resection combined with PV resection. However, occasional long-term survival could be observed after curative resection in patients with deep PV wall invasion.

[Analysis of a series of 100 mesenterico-portal vein resections during pancreatic resection]. / Analyse d'une série de 100 résections veineuses mésentérico-portales au cours des exérèses pancréatiques.

Pancreatic resection is currently the only treatment offering the possibility of long-term survival for patients with pancreatic cancer. Mesentericoportal vein involvement used to be considered a contraindication to pancreatic resection, but recent advances in vascular surgery have gradually extended the indications of curative pancreatic resection to such cases. We report hereby our experience of 100 pancreatic resections combined with mesentericoportal vein resection for pancreatic malignancies, performed between 1989 and 2005. This is one of the largest reported series. The overall mortality rate was 4% and the morbidity rate was 39%. Among the 76 patients who had pancreatic adenocarcinoma, the 5-year survival rate in case of limited mesenterico-portal vein wall involvement (up to the adventitia) was similar to that among patients without histological involvement of the portal vein wall (35.8% and 26.7%, respectively). These results support aggressive management consisting of resection and reconstruction of the mesentericoportal veins in patients with venous involvement, provided curative R0 resection is feasible.

In-column ATR-FTIR spectroscopy to monitor affinity chromatography purification of monoclonal antibodies.

In recent years many monoclonal antibodies (mAb) have entered the biotherapeutics market, offering new treatments for chronic and life-threatening diseases. Protein A resin captures monoclonal antibody (mAb) effectively, but the binding capacity decays over repeated purification cycles. On an industrial scale, replacing fouled Protein A affinity chromatography resin accounts for a large proportion of the raw material cost. Cleaning-in-place (CIP) procedures were developed to extend Protein A resin lifespan, but chromatograms cannot reliably quantify any remaining contaminants over repeated cycles. To study resin fouling in situ, we coupled affinity chromatography and Fourier transform infrared (FTIR) spectroscopy for the first time, by embedding an attenuated total reflection (ATR) sensor inside a micro-scale column while measuring the UV 280 nm and conductivity. Our approach quantified the in-column protein concentration in the resin bed and determined protein conformation. Our results show that Protein A ligand leached during CIP. We also found that host cell proteins bound to the Protein A resin even more strongly than mAbs and that typical CIP conditions do not remove all fouling contaminants. The insights derived from in-column ATR-FTIR spectroscopic monitoring could contribute to mAb purification quality assurance as well as guide the development of more effective CIP conditions to optimise resin lifespan.

Experimental models of acute and chronic liver failure in nude mice to study hepatocyte transplantation.

Although hepatocyte transplantation is a promising therapy for acute liver failure in human, there is still a lack of animal models suffering from hepatic injury in which the benefits of hepatocyte transplantation could be evaluated solely, without the bias caused by immunosuppression. As a consequence, the aim of the study was first to develop reproducible models of partial hepatectomy and of thioacetamide (TA)- or Jo2-induced acute liver failure in nude mice. Chronic liver disease was also investigated by repeated injections of sublethal doses of thioacetamide. Survival rates, routine histologic observations, alanin aminotransferase sera content, Ki67, and caspase 3 immunodetection were investigated both after 40% partial hepatectomy and after toxic-induced damages. Liver injuries were more severe and/or precocious in nude mice than in Balb/c mice for a given treatment with a maximum of acute injury obtained 24 h after single toxic injection, and were found to be transitory and reversible within 10 days. Toxics induced apoptosis followed by necrosis, confirming recent published data. Onset of fibrosis leading to reproducible chronic cirrhosis in nude mice correlated with increasing number of Ki67-positive cells, indicating that high levels of cell proliferation occurred. Chronic cirrhosis progressively reversed to fibrosis when the treatment ceased. Preliminary results demonstrated that engrafted xenogeneic hepatocytes could be detected in the host liver by anti-MHC class I immunohistochemistry. Fractions enriched in 2n or 4n hepatocytes by cell sorting using a flow cytometer were equivalent to the unpurified fraction in terms of engraftment in control nude mice or in nude mice subjected to PH. However, in mice suffering from liver injury 24 h after Jo2 or TA treatment, the engraftment of 2n hepatocytes was about twice that of an unpurified hepatocyte population or of a population enriched in 4n hepatocytes.

Oral efficacy of the new immunomodulator FTY720 in cynomolgus monkey kidney allotransplantation, given alone or in combination with cyclosporine or RAD.

BACKGROUND: FTY720 is a novel immunomodulator with a unique mechanism of action, i.e. chemokine-dependent lymphocyte homing into secondary lymphoid organs associated with profound lymphocyte depletion in blood. We investigated its efficacy, either FTY720 alone or together with cyclosporine or the rapamycin derivative rapamycin derivative (RAD), in cynomolgus monkey kidney allotransplantation. METHODS: Life-supporting allotransplantation was performed in bilaterally nephrectomized hosts. Compounds were given once daily by oral gavage. Monitoring was done by serum creatinine and urea, and rejection was concluded when values exceeded 500 micromol/L and 50 mmol/L, respectively (5-6 times the upper limit of reference values). Rejection was confirmed by graft histology. The termination point was set to 100 days after transplantation. In addition, animals were monitored for 24 hr drug concentrations and thorough inspection of potential adverse side effects. RESULTS: FTY720 given alone at 3.0 mg/kg per day prolonged rejection-free survival (33-85 days, mean 24 hr concentration between 54 and 66 ng/mL [n=3]), but it was not efficacious at a 0.3 mg/kg per day dose. For cyclosporine alone, 30 mg/kg per day during maintenance was efficacious (average concentration above 100 ng/mL, historical data from our group), and for RAD alone 0.75 mg/kg per day (concentration above 10 ng/mL). Efficacious FTY720-cyclosporine-A (CsA) or FTY720-RAD combinations were established using 0.1-0.3 mg/kg per day FTY720, 10-30 mg/kg per day cyclosporine, and/or 0.25-0.50 mg/kg per day RAD. Compared with single-compound treatment, FTY720 effective doses and 24 hr trough concentrations were at least tenfold lower in combination treatment and those of cyclosporine and RAD about twofold lower, indicative of effective synergy between the compounds. Already at the lowest FTY720 dose tested (0.03 mg/kg per day), there was a profound lymphocyte depletion down to about 30% of pretransplant values, which further increased at the highest dose (3.0 mg/kg per day, to about 14% of pretransplant values). Lymphocyte depletion was reflected by a decrease in T and B subpopulations. CONCLUSION: FTY720 is an effective immunosuppressant in prevention of acute kidney allograft rejection in cynomolgus monkeys and synergizes with cyclosporine and/or RAD in yielding rejection-free allograft survival.