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.

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.

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.

Differential Scanning Fluorimetry provides high throughput data on silk protein transitions.

Here we present a set of measurements using Differential Scanning Fluorimetry (DSF) as an inexpensive, high throughput screening method to investigate the folding of silk protein molecules as they abandon their first native melt conformation, dehydrate and denature into their final solid filament conformation. Our first data and analyses comparing silks from spiders, mulberry and wild silkworms as well as reconstituted 'silk' fibroin show that DSF can provide valuable insights into details of silk denaturation processes that might be active during spinning. We conclude that this technique and technology offers a powerful and novel tool to analyse silk protein transitions in detail by allowing many changes to the silk solutions to be tested rapidly with microliter scale sample sizes. Such transition mechanisms will lead to important generic insights into the folding patterns not only of silks but also of other fibrous protein (bio)polymers.

Silk protein aggregation kinetics revealed by Rheo-IR.

The remarkable mechanical properties of silk fibres stem from a multi-scale hierarchical structure created when an aqueous protein "melt" is converted to an insoluble solid via flow. To directly relate a silk protein's structure and function in response to flow, we present the first application of a Rheo-IR platform, which couples cone and plate rheology with attenuated total reflectance infrared spectroscopy. This technique provides a new window into silk processing by linking shear thinning to an increase in molecular alignment, with shear thickening affecting changes in the silk protein's secondary structure. Additionally, compared to other static characterization methods for silk, Rheo-IR proved particularly useful at revealing the intrinsic difference between natural (native) and reconstituted silk feedstocks. Hence Rheo-IR offers important novel insights into natural silk processing. This has intrinsic academic merit, but it might also be useful when designing reconstituted silk analogues alongside other polymeric systems, whether natural or synthetic.

Pathologic response to non-surgical locoregional therapies as potential selection criteria for liver transplantation for hepatocellular carcinoma.

BACKGROUND: Preoperative locoregional treatments (PLT) are performed to avoid progression before liver transplantation for hepatocellular carcinoma (HCC). The objective of this study was to analyze the prognostic factors affecting the outcome in patients who received PLT. MATERIAL AND METHODS: A retrospective analysis of patients who underwent liver transplantation (LT) was performed. All patients who underwent PLT with confirmed pathological diagnosis of HCC were included. The rate of tumor necrosis (TN) was assessed by microscopic histological examination. RESULTS: From January 1997 to December 2010, PLT was performed in 154 patients ROC analysis individuated a TN cut-off value at 40%. Ninety-one patients (59.1%) of the patients presented TN>40%. At multivariate analysis, TN<40% (HR=1.76; p=0.04) and vascular invasion (VI) (HR=2.16; p<0.01) were associated with lower Overall Survival (OS). At multivariate analysis, TN<40% (HR=1.59; p=0.001) and VI (HR=2.51; p=0.001) were significant associated with lower Disease Free Survival (DFS). One, 3 and 5 years OS was 87.9%, 82.0% and 69.1% for patients with TN>40% and 82.5%, 64.2% and 53.2% for those with TN<40% (p=0.02). Tumour size <5 cm (p=0.02); age <55 years (p=0.02); absence of VI (p=0.02) and multiple procedures (p=0.04) were predictive factors for TN>40%. CONCLUSIONS: Response to preoperative locoregional treatment can be used as potential selection criteria for LT.

Sotrastaurin (AEB071) alone and in combination with cyclosporine A prolongs survival times of non-human primate recipients of life-supporting kidney allografts.

BACKGROUND: Sotrastaurin (STN), a novel oral protein kinase C inhibitor that inhibits early T-cell activation, was assessed in non-human primate recipients of life-supporting kidney allografts. METHODS: Cynomolgus monkey recipients of life-supporting kidney allografts were treated orally with STN alone or in combination with cyclosporine A (CsA). RESULTS: STN monotherapy at 50 mg/kg once daily prolonged recipient survival times to the predefined endpoint of 29 days (n=2); when given at 25 mg/kg twice daily, the median survival time (MST) was 27 days (n=4). Neither once-daily monotherapy of STN 20 mg/kg nor CsA 20 mg/kg was effective (MST 6 days [n=2] and 7 days [n=5], respectively). In combination, however, STN 20 mg/kg and CsA 20 mg/kg prolonged MST to more than 100 days (n=5). By combining lower once-daily doses of STN (7 or 2 mg/kg) with CsA (20 mg/kg), MST was more than 100 (n=3) and 22 days (n=2), respectively. Neither in single-dose pharmacokinetic studies nor the transplant recipients were STN or CsA blood levels for combined treatment greater than when either drug was administered alone. STN blood levels in transplant recipients during combination therapy were dose related (20 mg/kg, 30-182 ng/mL; 7 mg/kg, 7-41 ng/mL; and 2 mg/kg, 3-5 ng/mL). STN at a daily dose of up to 20 mg/kg was relatively well tolerated. CONCLUSIONS: STN prolonged survival times of non-human primate kidney allograft recipients both as monotherapy and most effectively in combination with CsA. Pharmacokinetic interactions were not responsible for the potentiation of immunosuppressive efficacy by coadministering STN and CsA.

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.

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.

Successful liver transplantation for Rendu-Weber-Osler disease, a single centre experience.

UNLABELLED: BACKROUNDS/PURPOSE: Hereditary hemorrhagic telangiectasia or Rendu-Weber-Osler is an autosomal dominant inherited disorder characterized by arteriovenous malformations and telangiectasia that may affect the nose, skin, lungs, brain and gastrointestinal tract. Liver involvement of the disease has been described to be responsible of biliary tract necrosis, high cardiac output and portal hypertension, due to intra-hepatic vascular shunts. We aimed to present four cases of successful orthotopic liver transplantations in this indication performing our modified Piggy-back technique. PATIENTS AND METHODS: Between 2002 and 2008, four patients have been diagnosed for Rendu-Weber-Osler disease and underwent liver transplantation. Three of them suffered from high cardiac output with heart failure, two presented HBV infection and one patient suffered from renal failure requiring a liver-kidney transplantation. We performed our modified Piggy-back technique for liver implantation, which consists to clamp selectively the hepatic veins during the hepatectomy, without venous bypass, the retro-hepatic vena cava is preserved. RESULTS: No hemodynamic concerns disturbed the surgery and no massive transfusions were needed. The liver replacement corrected the cardiac insufficiency due to high cardiac output for the three patients. At present, the four patients are getting well. CONCLUSIONS: Despite new advances in immunotherapy for the medical treatment of Rendu-Weber-Osler disease, liver transplantation remains the curative option for hepatic based-hereditary hemorrhagic telangiectasia.

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.

Quantitative determination of band distortions in diamond attenuated total reflectance infrared spectra.

Due to its unmatched hardness and chemical inertia, diamond offers many advantages over other materials for extreme conditions and routine analysis by attenuated total reflection (ATR) infrared spectroscopy. Its low refractive index can offer up to a 6-fold absorbance increase compared to germanium. Unfortunately, it also results for strong bands in spectral distortions compared to transmission experiments. The aim of this paper is to present a methodological approach to determine quantitatively the degree of the spectral distortions in ATR spectra. This approach requires the determination of the optical constants (refractive index and extinction coefficient) of the investigated sample. As a typical example, the optical constants of the fibroin protein of the silk worm Bombyx mori have been determined from the polarized ATR spectra obtained using both diamond and germanium internal reflection elements. The positions found for the amide I band by germanium and diamond ATR are respectively 6 and 17 cm(-1) lower than the true value dtermined from the k(nu) spectrum, which is calculated to be 1659 cm(-1). To determine quantitatively the effect of relevant parameters such as the film thickness and the protein concentration, various spectral simulations have also been performed. The use of a thinner film probed by light polarized in the plane of incidence and diluting the protein sample can help in obtaining ATR spectra that are closer to their transmittance counterparts. To extend this study to any system, the ATR distortion amplitude has been evaluated using spectral simulations performed for bands of various intensities and widths. From these simulations, a simple empirical relationship has been found to estimate the band shift from the experimental band height and width that could be of practical use for ATR users. This paper shows that the determination of optical constants provides an efficient way to recover the true spectrum shape and band frequencies of distorted ATR spectra.

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.

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.

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.