PARIS undergoes liquid-liquid phase separation and poly(ADP-ribose)-mediated solidification.

ZNF746 was identified as parkin-interacting substrate (PARIS). Investigating its pathophysiological properties, we find that PARIS undergoes liquid-liquid phase separation (LLPS) and amorphous solid formation. The N-terminal low complexity domain 1 (LCD1) of PARIS is required for LLPS, whereas the C-terminal prion-like domain (PrLD) drives the transition from liquid to solid phase. In addition, we observe that poly(ADP-ribose) (PAR) strongly binds to the C-terminus of PARIS near the PrLD, accelerating its LLPS and solidification. N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced PAR formation leads to PARIS oligomerization in human iPSC-derived dopaminergic neurons that is prevented by the PARP inhibitor, ABT-888. Furthermore, SDS-resistant PARIS species are observed in the substantia nigra (SN) of aged mice overexpressing wild-type PARIS, but not with a PAR binding-deficient PARIS mutant. PARIS solidification is also found in the SN of mice injected with preformed fibrils of α-synuclein (α-syn PFF) and adult mice with a conditional knockout (KO) of parkin, but not if α-syn PFF is injected into mice deficient for PARP1. Herein, we demonstrate that PARIS undergoes LLPS and PAR-mediated solidification in models of Parkinson's disease.

Alveolar Stretch Activation of Endothelial Piezo1 Protects Adherens Junctions and Lung Vascular Barrier.

Disruption of alveolar-capillary barriers is a major complication of high-volume mechanical ventilation referred to as "ventilator-induced lung injury." The stretching force in alveoli is transmitted to endothelial cells, increasing the tension on underlying endothelial plasma membrane. The mechanosensor Piezo1, a plasma membrane cation channel, was inducibly deleted in endothelial cells of mice (Piezo1iEC-/-), which allowed us to study its role in regulating the endothelial barrier response to alveolar stretch. We observed significant increase in lung vascular permeability in Piezo1iEC-/- mice as compared with control Piezo1fl/fl mice in response to high-volume mechanical ventilation. We also observed that human lung endothelial monolayers depleted of Piezo1 and exposed to cyclic stretch had increased permeability. We identified the calcium-dependent cysteine protease calpain as a downstream target of Piezo1. Furthermore, we showed that calpain maintained stability of the endothelial barrier in response to mechanical stretch by cleaving Src kinase, which was responsible for disassembling endothelial adherens junctions. Pharmacological activation of calpain caused Src cleavage and thereby its inactivation, and it restored the disrupted lung endothelial barrier seen in Piezo1iEC-/- mice undergoing high-volume mechanical ventilation. Our data demonstrate that downregulation of Piezo1 signaling in endothelium is a critical factor in the pathogenesis of ventilator-induced lung injury, and thus augmenting Piezo1 expression or pharmacologically activating Piezo1 signaling may be an effective therapeutic strategy.

Piezo1 mediates angiogenesis through activation of MT1-MMP signaling.

Angiogenesis is initiated in response to a variety of external cues, including mechanical and biochemical stimuli; however, the underlying signaling mechanisms remain unclear. Here, we investigated the proangiogenic role of the endothelial mechanosensor Piezo1. Genetic deletion and pharmacological inhibition of Piezo1 reduced endothelial sprouting and lumen formation induced by wall shear stress and proangiogenic mediator sphingosine 1-phosphate, whereas Piezo1 activation by selective Piezo1 activator Yoda1 enhanced sprouting angiogenesis. Similarly to wall shear stress, sphingosine 1-phosphate functioned by activating the Ca2+ gating function of Piezo1, which in turn signaled the activation of the matrix metalloproteinase-2 and membrane type 1 matrix metalloproteinase during sprouting angiogenesis. Studies in mice in which Piezo1 was conditionally deleted in endothelial cells demonstrated the requisite role of sphingosine 1-phosphate-dependent activation of Piezo1 in mediating angiogenesis in vivo. These results taken together suggest that both mechanical and biochemical stimuli trigger Piezo1-mediated Ca2+ influx and thereby activate matrix metalloproteinase-2 and membrane type 1 matrix metalloproteinase and synergistically facilitate sprouting angiogenesis.

Tuning the electronic structure of single-walled carbon nanotube by high-pressure H2 exposure.

We report on an electronic structure change of single-walled carbon nanotube (SWNT) on hexagonal boron nitride due to electron doping via high-pressure H2 exposure. The fractional coverage of hydrogenated carbon atom is estimated to be at least θ = 0.163 from the in situ I ds-V g measurements of the release process. Raman spectroscopy and x-ray photoelectron spectroscopy were carried out to support the in situ electrical measurements. In particular, we used the dissociative Langmuir-type model to yield the desorption coefficient k des by fitting it to the in situ electrical data. Finally, we applied this hydrogenation method to the SWNT network on the commercial Si/SiO2 substrate to open the possibility of the scalable n-type semiconducting SWNT FETs.

PARIS reprograms glucose metabolism by HIF-1α induction in dopaminergic neurodegeneration.

Our previous study found that PARIS (ZNF746) transcriptionally suppressed transketolase (TKT), a key enzyme in pentose phosphate pathway (PPP) in the substantia nigra (SN) of AAV-PARIS injected mice. In this study, we revealed that PARIS overexpression reprogrammed glucose metabolic pathway, leading to the increment of glycolytic proteins along with TKT reduction in the SN of AAV-PARIS injected mice. Knock-down of TKT in differentiated SH-SY5Y cells led to an increase of glycolytic enzymes and decrease of PPP-related enzymes whereas overexpression of TKT restored PARIS-mediated glucose metabolic shift, suggesting that glucose metabolic alteration by PARIS is TKT-dependent. Inhibition of PPP by either PARIS overexpression or TKT knock-down elevated the level of H2O2, and diminished NADPH and GSH levels, ultimately triggering the induction of HIF-1α, a master activator of glycolysis. In addition, TKT inhibition by stereotaxic injection of oxythiamine demonstrated slight decrement of dopaminergic neurons (DNs) in SN but not cortical neurons in the cortex, suggesting that TKT might be a survival factor of DNs. In differentiated SH-SY5Y, cell toxicity by GFP-PARIS was partially restored by introduction of Flag-TKT and siRNA-HIF-1α. We also observed the increase of HIF-1α and glycolytic hexokinase 2 in the SN of Parkinson's disease patients. Taken together, these results suggest that PARIS accumulation might distort the balance of glucose metabolism, providing clues for understanding mechanism underlying selective DNs death by PARIS.

Antiangiogenic Therapeutic Potential of Peptides Derived from the Molecular Motor KIF13B that Transports VEGFR2 to Plasmalemma in Endothelial Cells.

Vascular endothelial growth factor receptor 2 (VEGFR2) localized on the surface of endothelial cells (ECs) is a key determinant of the magnitude and duration of angiogenesis induced by vascular endothelial growth factor (VEGF). The kinesin family plus-end motor KIF13B transports VEGFR2 to the EC surface, and as such, specific inhibition of polarized VEGFR2 trafficking prevents angiogenesis. We designed a series of bioactive peptides based on deep analysis of VEGFR2-binding domain of KIF13B that compete specifically with VEGFR2 binding of KIF13B and thereby potently inhibit angiogenesis. Expression of these peptides by lentivirus prevents VEGF-induced capillary network formation in Matrigel plugs and neovascularization in vivo. A synthetic soluble, cell-permeable, 23-amino acid peptide termed kinesin-derived angiogenesis inhibitor (KAI) not only prevents interaction of VEGFR2 with KIF13B but also trafficking of VEGFR2 in the plus-end direction to the EC plasmalemma. Kinesin-derived angiogenesis inhibitor also inhibits VEGF-induced EC migration and tumor growth in human lung carcinoma xenografted in immunodeficient mice. Thus, we describe a novel class of peptides derived from the site of interaction of KIF13B with VEGFR2 that inhibit VEGFR2 trafficking and thereby starve cancer of blood supply.

Identification of transketolase as a target of PARIS in substantia nigra.

Recently, PARIS (ZNF746) is introduced as authentic substrate of parkin and transcriptionally represses PGC-1α by binding to insulin responsive sequences (IRSs) in the promoter of PGC-1α. The overexpression of PARIS selectively leads to the loss of dopaminergic neurons (DN) and mitochondrial abnormalities in the substantia nigra (SN) of Parkinson's disease (PD) models. To identify PARIS target molecules altered in SN region-specific manner, LC-MS/MS-based quantitative proteomic analysis is employed to investigate proteomic alteration in the cortex, striatum, and SN of AAV-PARIS injected mice. Herein, we find that the protein and mRNA of transketolase (TKT), a key enzyme in pentose phosphate pathway (PPP) of glucose metabolism, is exclusively decreased in the SN of AAV-PARIS mice. PARIS overexpression suppresses TKT transcription via IRS-like motif in the TKT promoter. Moreover, the reduction of TKT by PARIS is found in primary DN but not in cortical neurons, suggesting that PARIS-medicated TKT suppression is cell type-dependent. Interestingly, we observe the reduced level of TKT in the SN of PD patients but not in the cortex. These findings indicate that TKT might be a SN-specific target of PARIS, providing new clues to understand the mechanism underlying selective DNs death in PD.

Repression of rRNA transcription by PARIS contributes to Parkinson's disease.

The nucleolus is a compartment for the transcription of ribosomal RNA (rRNA) and assembly of ribosome subunits. Dysregulation of the nucleolus is considered to be a cellular stress event associated with aging and neurodegenerative disease, including Parkinson's disease (PD). We previously demonstrated that PARIS (PARkin Interacting Substrate, ZNF746) transcriptionally suppresses peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1α (PGC-1α) in PD and its accumulation results in selective dopaminergic neuronal death. However, functional knowledge of PARIS is limited, and no other studies have been performed to elucidate its function. Here, we used tandem-affinity purification to identify the binding partners of PARIS, showing that PARIS interacts with 160-kDa Myb-binding protein 1α (MYBBP1A), which suppresses rRNA transcription and the rRNA editing process. Interestingly, PARIS was also found to interact with the components of RNA polymerase I, occupied the promoter of rDNA, and suppressed rDNA transcription in vivo. Accordingly, we observed a reduction of rRNA levels and increased expression of p53, a molecular marker of nucleolar stress, in the substantia nigra of conditional parkin knockout mice, AAV-mediated PARIS overexpression mice, and in patients with sporadic PD. Together, our results suggest that dysfunction of the Parkin-PARIS pathway may play a deleterious role in rRNA transcription and contribute to PD pathogenesis.

Fluid shear stress promotes proprotein convertase-dependent activation of MT1-MMP.

During angiogenesis, endothelial cells (ECs(1)) initiate new blood vessel growth and invade into the extracellular matrix (ECM). Membrane type-1 matrix metalloproteinase (MT1-MMP) facilitates this process and translocates to the plasma membrane following activation to promote ECM cleavage. The N-terminal pro-domain within MT1-MMP must be processed for complete activity of the proteinase. This study investigated whether MT1-MMP activation was altered by sphingosine 1-phosphate (S1P) and wall shear stress (WSS), which combine to stimulate EC invasion in three dimensional (3D) collagen matrices. MT1-MMP was activated rapidly and completely by WSS but not S1P. Proprotein convertases (PCs) promoted MT1-MMP processing, prompting us to test whether WSS or S1P treatments increased PC activity. Like MT1-MMP, PC activity increased with WSS, while S1P had no effect. A pharmacological PC inhibitor completely blocked S1P- and WSS-induced EC invasion and MT1-MMP translocation to the plasma membrane. Further, a recombinant PC inhibitor reduced MT1-MMP activation and decreased lumen formation in invading ECs, a process known to be controlled by MT1-MMP. Thus, we conclude that PC and MT1-MMP activation are mechanosensitive events that are required for EC invasion into 3D collagen matrices.

Proteomic profiling of endothelial invasion revealed receptor for activated C kinase 1 (RACK1) complexed with vimentin to regulate focal adhesion kinase (FAK).

Angiogenesis is critical for many physiological and pathological processes. To identify molecules relevant to angiogenesis, we performed a proteomic screen comparing invading versus non-invading endothelial cells in three-dimensional collagen matrices. We found up-regulated levels of receptor for activated C kinase 1 (RACK1) and the intermediate filament protein vimentin that correlated with increased endothelial cell invasion. Because both RACK1 and vimentin have been linked to focal adhesion kinase (FAK), we investigated whether this pathway regulated invasion. RACK1 depletion reduced invasion responses, and this was associated with attenuated activation of FAK. Knockdown of vimentin significantly decreased levels of phosphorylated and total FAK. Treatment with a pharmacological inhibitor of FAK dose-dependently reduced invasion, indicating a crucial role for FAK activity during invasion. Because RACK1 and vimentin were both up-regulated with sphingosine 1-phosphate treatment, required for invasion, and regulated FAK, we tested whether they complexed together. RACK1 complexed with vimentin, and growth factors enhanced this interaction. In addition, RACK1, vimentin, and FAK formed an intermolecular complex in invading endothelial cultures in three dimensions in response to stimulation by sphingosine 1-phosphate and growth factors. Moreover, depletion of RACK1 decreased the association of vimentin and FAK, suggesting that RACK1 was required for stabilizing vimentin-FAK interactions during sprouting. Silencing of vimentin and RACK1 decreased cell adhesion and focal contact formation. Taken together, these results demonstrate that proangiogenic signals converge to enhance expression and association of RACK1 and vimentin, which regulated FAK, resulting in successful endothelial sprout formation in three-dimensional collagen matrices.

Insight into Defect Engineering of Atomically Dispersed Iron Electrocatalysts for High-Performance Proton Exchange Membrane Fuel Cell.

Atomically dispersed and nitrogen coordinated iron catalysts (Fe-NCs) demonstrate potential as alternatives to platinum-group metal (PGM) catalysts in oxygen reduction reaction (ORR). However, in the context of practical proton exchange membrane fuel cell (PEMFC) applications, the membrane electrode assembly (MEA) performances of Fe-NCs remain unsatisfactory. Herein, improved MEA performance is achieved by tuning the local environment of the Fe-NC catalysts through defect engineering. Zeolitic imidazolate framework (ZIF)-derived nitrogen-doped carbon with additional CO2 activation is employed to construct atomically dispersed iron sites with a controlled defect number. The Fe-NC species with the optimal number of defect sites exhibit excellent ORR performance with a high half-wave potential of 0.83 V in 0.5 M H2 SO4 . Variation in the number of defects allows for fine-tuning of the reaction intermediate binding energies by changing the contribution of the Fe d-orbitals, thereby optimizing the ORR activity. The MEA based on a defect-engineered Fe-NC catalyst is found to exhibit a remarkable peak power density of 1.1 W cm-2 in an H2 /O2 fuel cell, and 0.67 W cm-2  in an H2 /air fuel cell, rendering it one of the most active atomically dispersed catalyst materials at the MEA level.

Farnesol prevents aging-related muscle weakness in mice through enhanced farnesylation of Parkin-interacting substrate.

Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) is a master regulator of mitochondrial biogenesis. Reduced PGC-1α abundance is linked to skeletal muscle weakness in aging or pathological conditions, such as neurodegenerative diseases and diabetes; thus, elevating PGC-1α abundance might be a promising strategy to treat muscle aging. Here, we performed high-throughput screening and identified a natural compound, farnesol, as a potent inducer of PGC-1α. Farnesol administration enhanced oxidative muscle capacity and muscle strength, leading to metabolic rejuvenation in aged mice. Moreover, farnesol treatment accelerated the recovery of muscle injury associated with enhanced muscle stem cell function. The protein expression of Parkin-interacting substrate (PARIS/Zfp746), a transcriptional repressor of PGC-1α, was elevated in aged muscles, likely contributing to PGC-1α reduction. The beneficial effect of farnesol on aged muscle was mediated through enhanced PARIS farnesylation, thereby relieving PARIS-mediated PGC-1α suppression. Furthermore, short-term exercise increased PARIS farnesylation in the muscles of young and aged mice, whereas long-term exercise decreased PARIS expression in the muscles of aged mice, leading to the elevation of PGC-1α. Collectively, the current study demonstrated that the PARIS-PGC-1α pathway is linked to muscle aging and that farnesol treatment can restore muscle functionality in aged mice through increased farnesylation of PARIS.

Fluid shear stress and sphingosine 1-phosphate activate calpain to promote membrane type 1 matrix metalloproteinase (MT1-MMP) membrane translocation and endothelial invasion into three-dimensional collagen matrices.

The vascular endothelium continually senses and responds to biochemical and mechanical stimuli to appropriately initiate angiogenesis. We have shown previously that fluid wall shear stress (WSS) and sphingosine 1-phosphate (S1P) cooperatively initiate the invasion of human umbilical vein endothelial cells into collagen matrices (Kang, H., Bayless, K. J., and Kaunas, R. (2008) Am. J. Physiol. Heart Circ. Physiol. 295, H2087-2097). Here, we investigated the role of calpains in the regulation of endothelial cell invasion in response to WSS and S1P. Calpain inhibition significantly decreased S1P- and WSS-induced invasion. Short hairpin RNA-mediated gene silencing demonstrated that calpain 1 and 2 were required for WSS and S1P-induced invasion. Also, S1P synergized with WSS to induce invasion and to activate calpains and promote calpain membrane localization. Calpain inhibition results in a cell morphology consistent with reduced matrix proteolysis. Membrane type 1-matrix metalloproteinase (MT1-MMP) has been shown by others to regulate endothelial cell invasion, prompting us to test whether calpain acted upstream of MT1-MMP. S1P and WSS synergistically activated MT1-MMP and induced cell membrane localization of MT1-MMP in a calpain-dependent manner. Calpain activation, MT1-MMP activation and MT1-MMP membrane localization were all maximal with 5.3 dynes/cm(2) WSS and S1P treatment, which correlated with maximal invasion responses. Our data show for the first time that 5.3 dynes/cm(2) WSS in the presence of S1P combine to activate calpains, which direct MT1-MMP membrane localization to initiate endothelial sprouting into three-dimensional collagen matrices.

Calpain-mediated vimentin cleavage occurs upstream of MT1-MMP membrane translocation to facilitate endothelial sprout initiation.

Endothelial cells normally line the vasculature and remain quiescent. However, these cells can be rapidly stimulated to undergo morphogenesis and initiate new blood vessel formation given the proper cues. This study reports a new mechanism for initiating angiogenic sprout formation that involves vimentin, the major intermediate filament protein in endothelial cells. Initial studies confirmed vimentin was required for sphingosine 1-phosphate (S1P)- and growth factor (GF)-induced endothelial cell invasion, and vimentin was cleaved by calpains during invasion. Calpains were predominantly activated by GF and were required for sprout initiation. Because others have reported membrane type 1-matrix metalloproteinase (MT1-MMP) is required for endothelial sprouting responses, we tested whether vimentin and calpain acted upstream of MT1-MMP. Both calpain and vimentin were required for successful MT1-MMP membrane translocation, which was stimulated by S1P. In addition, vimentin complexed with MT1-MMP in a manner that required both the cytoplasmic domain of MT1-MMP and calpain activation, which increased the soluble pool of vimentin in endothelial cells. Altogether, these data indicate that pro-angiogenic signals converge to activate calpain-dependent vimentin cleavage and increase vimentin solubility, which act upstream to facilitate MT1-MMP membrane translocation, resulting in successful endothelial sprout formation in three-dimensional collagen matrices. These findings help explain why S1P and GF synergize to stimulate robust sprouting in 3D collagen matrices.

Loss of zinc-finger protein 212 leads to Purkinje cell death and locomotive abnormalities with phospholipase D3 downregulation.

Although Krüppel-associated box domain-containing zinc-finger proteins (K-ZNFs) may be associated with sophisticated gene regulation in higher organisms, the physiological functions of most K-ZNFs remain unknown. The Zfp212 protein was highly conserved in mammals and abundant in the brain; it was mainly expressed in the cerebellum (Cb). Zfp212 (mouse homolog of human ZNF212) knockout (Zfp212-KO) mice showed a reduction in survival rate compared to wild-type mice after 20 months of age. GABAergic Purkinje cell degeneration in the Cb and aberrant locomotion were observed in adult Zfp212-KO mice. To identify genes related to the ataxia-like phenotype of Zfp212-KO mice, 39 ataxia-associated genes in the Cb were monitored. Substantial alterations in the expression of ataxin 10, protein phosphatase 2 regulatory subunit beta, protein kinase C gamma, and phospholipase D3 (Pld3) were observed. Among them, Pld3 alone was tightly regulated by Flag-tagged ZNF212 overexpression or Zfp212 knockdown in the HT22 cell line. The Cyclic Amplification and Selection of Targets assay identified the TATTTC sequence as a recognition motif of ZNF212, and these motifs occurred in both human and mouse PLD3 gene promoters. Adeno-associated virus-mediated introduction of human ZNF212 into the Cb of 3-week-old Zfp212-KO mice prevented Purkinje cell death and motor behavioral deficits. We confirmed the reduction of Zfp212 and Pld3 in the Cb of an alcohol-induced cerebellar degeneration mouse model, suggesting that the ZNF212-PLD3 relationship is important for Purkinje cell survival.

PARIS farnesylation prevents neurodegeneration in models of Parkinson's disease.

Accumulation of the parkin-interacting substrate (PARIS; ZNF746), due to inactivation of parkin, contributes to Parkinson's disease (PD) through repression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α; PPARGC1A) activity. Here, we identify farnesol as an inhibitor of PARIS. Farnesol promoted the farnesylation of PARIS, preventing its repression of PGC-1α via decreasing PARIS occupancy on the PPARGC1A promoter. Farnesol prevented dopaminergic neuronal loss and behavioral deficits via farnesylation of PARIS in PARIS transgenic mice, ventral midbrain transduction of AAV-PARIS, adult conditional parkin KO mice, and the α-synuclein preformed fibril model of sporadic PD. PARIS farnesylation is decreased in the substantia nigra of patients with PD, suggesting that reduced farnesylation of PARIS may play a role in PD. Thus, farnesol may be beneficial in the treatment of PD by enhancing the farnesylation of PARIS and restoring PGC-1α activity.

Activation of the Akt1-CREB pathway promotes RNF146 expression to inhibit PARP1-mediated neuronal death.

Progressive degeneration of dopaminergic neurons characterizes Parkinson's disease (PD). This neuronal loss occurs through diverse mechanisms, including a form of programmed cell death dependent on poly(ADP-ribose) polymerase-1 (PARP1) called parthanatos. Deficient activity of the kinase Akt1 and aggregation of the protein α-synuclein are also implicated in disease pathogenesis. Here, we found that Akt1 suppressed parthanatos in dopaminergic neurons through a transcriptional mechanism. Overexpressing constitutively active Akt1 in SH-SY5Y cells or culturing cells with chlorogenic acid (a polyphenol found in coffee that activates Akt1) stimulated the CREB-dependent transcriptional activation of the gene encoding the E3 ubiquitin ligase RNF146. RNF146 inhibited PARP1 not through its E3 ligase function but rather by binding to and sequestering PAR, which enhanced the survival of cultured cells exposed to the dopaminergic neuronal toxin 6-OHDA or α-synuclein aggregation. In mice, intraperitoneal administration of chlorogenic acid activated the Akt1-CREB-RNF146 pathway in the brain and provided neuroprotection against both 6-OHDA and combinatorial α-synucleinopathy in an RNF146-dependent manner. Furthermore, dysregulation of the Akt1-CREB pathway was observed in postmortem brain samples from patients with PD. The findings suggest that therapeutic restoration of RNF146 expression, such as by activating the Akt1-CREB pathway, might halt neurodegeneration in PD.

Septin2 mediates podosome maturation and endothelial cell invasion associated with angiogenesis.

Podosomes are compartmentalized actin-rich adhesions, defined by their ability to locally secrete proteases and remodel extracellular matrix. Matrix remodeling by endothelial podosomes facilitates invasion and thereby vessel formation. However, the mechanisms underlying endothelial podosome formation and function remain unclear. Here, we demonstrate that Septin2, Septin6, and Septin7 are required for maturation of nascent endothelial podosomes into matrix-degrading organelles. We show that podosome development occurs through initial mobilization of the scaffolding protein Tks5 and F-actin accumulation, followed by later recruitment of Septin2. Septin2 localizes around the perimeter of podosomes in close proximity to the basolateral plasma membrane, and phosphoinositide-binding residues of Septin2 are required for podosome function. Combined, our results suggest that the septin cytoskeleton forms a diffusive barrier around nascent podosomes to promote their maturation. Finally, we show that Septin2-mediated regulation of podosomes is critical for endothelial cell invasion associated with angiogenesis. Therefore, targeting of Septin2-mediated podosome formation is a potentially attractive anti-angiogenesis strategy.

Author Correction: Apparent Power Law Scaling of Variable Range Hopping Conduction in Carbonized Polymer Nanofibers.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Probing variable range hopping lengths by magneto conductance in carbonized polymer nanofibers.

Using magneto transport, we probe hopping length scales in the variable range hopping conduction of carbonized polyacetylene and polyaniline nanofibers. In contrast to pristine polyacetylene nanofibers that show vanishing magneto conductance at large electric fields, carbonized polymer nanofibers display a negative magneto conductance that decreases in magnitude but remains finite with respect to the electric field. We show that this behavior of magneto conductance is an indicator of the electric field and temperature dependence of hopping length in the gradual transition from the thermally activated to the activation-less electric field driven variable range hopping transport. This reveals magneto transport as a useful tool to probe hopping lengths in the non-linear hopping regime.