Evaluation of Meniscal Regeneration in a Mini Pig Model Treated With a Novel Polyglycolic Acid Meniscal Scaffold

BACKGROUND

Meniscal injury is a severe impediment to movement and results in accelerated deterioration of the knee joint.

PURPOSE

To evaluate the effect of a novel meniscal scaffold prepared from polyglycolic acid coated with polylactic acid/caprolactone on the treatment of meniscal injury in a mini pig model.

STUDY DESIGN

Controlled laboratory study.

METHODS

The model was established with a 10-mm resection at the anterior medial meniscus on both knee joints. A scaffold was implanted in the right knee joint. The meniscal scaffold was inserted and sutured next to the native meniscus. The histological analysis was performed to determine meniscal regeneration with safranin O staining, cell proliferation with PCNA, inflammation with TNF, and collagen structure and production with picrosirius red and immunofluorescence. Cartilage degeneration was evaluated with Safranin O. Meniscal regeneration and joint fluid were evaluated with magnetic resonance imaging.

RESULTS

Although compressive stress and elastic modulus were significantly lower in the scaffold than in the native porcine menisci, ultimate tensile stress was similar. Implanted scaffolds were covered with tissue beginning at 4 weeks, with increased migration of proliferating cells to the implant area at 4 and 8 weeks. Scaffolds were absorbed with freshly produced collagen at 24 weeks. Cartilage degeneration was significantly lower in the meniscus-implanted group than in the meniscectomy group. Magnetic resonance imaging results did not show severe accumulation of joint fluids, suggesting negligible inflammation. Density of the implanted menisci was comparable with that of the native menisci.

CONCLUSION

Meniscal scaffold prepared from polyglycolic acid has therapeutic potential for meniscal regeneration.

CLINICAL RELEVANCE

This meniscal scaffold can improve biological knee reconstruction and prevent the increase of total knee arthroplasty.

Synthesis of neuraminidase-resistant sialoside-modified three-way junction DNA and its binding ability to various influenza viruses

Natural sialic acid-modified compounds are capable of targeting influenza virus hemagglutinin (HA). However, these compounds have limited inhibitory effect because natural O-glycoside bond in these compounds are prone to be cleaved by neuraminidase (NA) on the surface of viruses. In this study, we synthesized NA-resistant sialoside that included unnatural S-glycoside bonds and modified this sialoside on a three-way junction (3WJ) DNA to display complementary distribution to its binding sites on a HA trimer. This S-glycoside-containing sialoside-modified 3WJ DNA showed certain NA resistance and maintained high binding affinity. Importantly, our observations showed that substituting natural O-glycoside with unnatural S-glycoside did not affect the binding affinity of the sialoside-modified 3WJ DNA for viruses. Thus, this study is an important step forward in the development of NA-resistant sialoside derivatives for more effective detection and inhibition of infection by a broad spectrum of viruses.

Antiviral Mechanism of Action of Epigallocatechin-3-O-gallate and Its Fatty Acid Esters

Epigallocatechin-3-O-gallate (EGCG) is the major catechin component of green tea (Cameria sinensis), and is known to possess antiviral activities against a wide range of DNA viruses and RNA viruses. However, few studies have examined chemical modifications of EGCG in terms of enhanced antiviral efficacy. This paper discusses which steps of virus infection EGCG interferes with, citing previous reports. EGCG appears most likely to inhibits the early stage of infections, such as attachment, entry, and membrane fusion, by interfering with viral membrane proteins. According to the relationships between structure and antiviral activity of catechin derivatives, the 3-galloyl and 5'-OH group of catechin derivatives appear critical to antiviral activities. Enhancing the binding affinity of EGCG to virus particles would thus be important to increase virucidal activity. We propose a newly developed EGCG-fatty acid derivative in which the fatty acid on the phenolic hydroxyl group would be expected to increase viral and cellular membrane permeability. EGCG-fatty acid monoesters showed improved antiviral activities against different types of viruses, probably due to their increased affinity for virus and cellular membranes. Our study promotes the application of EGCG-fatty acid derivatives for the prevention and treatment of viral infections.

Sialyllactose-Modified Three-Way Junction DNA as Binding Inhibitor of Influenza Virus Hemagglutinin

Sialic acid present on the cell surface is recognized by hemagglutinin (HA) on the influenza virus in the first step of infection. Therefore, a compound that can efficiently interfere with the interaction between sialic acid and HA might inhibit infection and allow detection of the influenza virus. We focused on the spatial arrangement of sialic acid binding sites on HA and developed 2,3-sialyllactose (2,3-SL)-modified three-way junction (3WJ) DNA molecules with a topology similar to that of sialic acid binding sites. 3WJ DNA with three 2,3-SL residues on each DNA strand showed (8.0 × 10⁴)-fold higher binding affinity for influenza virus A/Puerto Rico/08/34 (H1N1) compared to the 2,3-SL. This result indicated that the glycocluster effect due to clustering on one DNA arm and optimal spatial arrangement of the 3WJ DNA improved the weak interactions between a sialic acid and its binding site on HA. This 3WJ DNA compound has possible application as an inhibitor of influenza infection and for virus sensing.

Design of Tail-Clamp Peptide Nucleic Acid Tethered with Azobenzene Linker for Sequence-Specific Detection of Homopurine DNA

DNA carries genetic information in its sequence of bases. Synthetic oligonucleotides that can sequence-specifically recognize a target gene sequence are a useful tool for regulating gene expression or detecting target genes. Among the many synthetic oligonucleotides, tail-clamp peptide nucleic acid (TC-PNA) offers advantages since it has two homopyrimidine PNA strands connected via a flexible ethylene glycol-type linker that can recognize complementary homopurine sequences via Watson-Crick and Hoogsteen base pairings and form thermally-stable PNA/PNA/DNA triplex structures. Here, we synthesized a series of TC-PNAs that can possess different lengths of azobenzene-containing linkers and studied their binding behaviours to homopurine single-stranded DNA. Introduction of azobenzene at the N-terminus amine of PNA increased the thermal stability of PNA-DNA duplexes. Further extension of the homopyrimidine PNA strand at the N-terminus of PNA-AZO further increased the binding stability of the PNA/DNA/PNA triplex to the target homopurine sequence; however, it induced TC-PNA/DNA/TC-PNA complex formation. Among these TC-PNAs, 9W5H-C4-AZO consisting of nine Watson-Crick bases and five Hoogsteen bases tethered with a beta-alanine conjugated azobenzene linker gave a stable 1:1 TC-PNA/ssDNA complex and exhibited good mismatch recognition. Our design for TC-PNA-AZO can be utilized for detecting homopurine sequences in various genes.

Substitution at the C-3 Position of Catechins Has an Influence on the Binding Affinities against Serum Albumin

It is known that catechins interact with the tryptophan (Trp) residue at the drug-binding site of serum albumin. In this study, we used catechin derivatives to investigate which position of the catechin structure strongly influences the binding affinity against bovine serum albumin (BSA) and human serum albumin (HSA). A docking simulation showed that (-)-epigallocatechin gallate (EGCg) interacted with both Trp residues of BSA (one at drug-binding site I and the other on the molecular surface), mainly by π-π stacking. Fluorescence analysis showed that EGCg and substituted EGCg caused a red shift of the peak wavelength of Trp similarly to warfarin (a drug-binding site I-specific compound), while 3-O-acyl-catechins caused a blue shift. To evaluate the binding affinities, the quenching constants were determined by the Stern-Volmer equation. A gallate ester at the C-3 position increased the quenching constants of the catechins. Against BSA, acyl substitution increased the quenching constant proportionally to the carbon chain lengths of the acyl group, whereas methyl substitution decreased the quenching constant. Against HSA, neither acyl nor methyl substitution affected the quenching constant. In conclusion, substitution at the C-3 position of catechins has an important influence on the binding affinity against serum albumin.

A derivative of epigallocatechin-3-gallate induces apoptosis via SHP-1-mediated suppression of BCR-ABL and STAT3 signalling in chronic myelogenous leukaemia

BACKGROUND AND PURPOSE

Epigallocatechin-3-gallate (EGCG) is a component of green tea known to have chemo-preventative effects on several cancers. However, EGCG has limited clinical application, which necessitates the development of a more effective EGCG prodrug as an anticancer agent.

EXPERIMENTAL APPROACH

Derivatives of EGCG were evaluated for their stability and anti-tumour activity in human chronic myeloid leukaemia (CML) K562 and KBM5 cells.

KEY RESULTS

EGCG-mono-palmitate (EGCG-MP) showed most prolonged stability compared with other EGCG derivatives. EGCG-MP exerted greater cytotoxicity and apoptosis in K562 and KBM5 cells than the other EGCG derivatives. EGCG-MP induced Src-homology 2 domain-containing tyrosine phosphatase 1 (SHP-1) leading decreased oncogenic protein BCR-ABL and STAT3 phosphorylation in CML cells, compared with treatment with EGCG. Furthermore, EGCG-MP reduced phosphorylation of STAT3 and survival genes in K562 cells, compared with EGCG. Conversely, depletion of SHP-1 or application of the tyrosine phosphatase inhibitor pervanadate blocked the ability of EGCG-MP to suppress phosphorylation of BCR-ABL and STAT3, and the expression of survival genes downstream of STAT3. In addition, EGCG-MP treatment more effectively suppressed tumour growth in BALB/c athymic nude mice compared with untreated controls or EGCG treatment. Immunohistochemistry revealed increased caspase 3 and SHP-1 activity and decreased phosphorylation of BCR-ABL in the EGCG-MP-treated group relative to that in the EGCG-treated group.

CONCLUSIONS AND IMPLICATIONS

EGCG-MP induced SHP-1-mediated inhibition of BCR-ABL and STAT3 signalling in vitro and in vivo more effectively than EGCG. This derivative may be a potent chemotherapeutic agent for CML treatment.

Abstract 5408: Liposomal doxorubicin with modified EGCG increased antitumor activity by topical targeting efficiency into tumor

Purpose: The aim of this study is increase of antitumor activity

using novel liposome with (-)-epigallocatechin-3-gallate (EGCG) as one of the green tea components. Liposome has been known as a one of useful drug carriers for delivering drug into targeting site. Moreover, some ligand is able to modify around liposomal membrane by a simple method. On the other hand, it was reported that surface of high grade tumor cell expresses 67kDa laminin receptor (67LR) which intermediates of cytostatic effect of EGCG, and EGCG is able to induce apoptosis selectively. Our strategy was to prepare liposomal doxorubicin with EGCG as carrier ligand for getting antitumor activity by both apoptosis and doxorubicin at tumor site. In this study, we tried to prepare EGCG-modified liposome and evaluated the antitumor activity in vitro.

Methods: The liposomal doxorubicin was prepared by L-α-distearoylphosphatidylcholine, cholesterol, L-α-distearoylphosphatidyl-DL-glycerol and doxorubicin (100:100:60:18 μmol). Doxorubicin included EGCG-modified liposome (EL-DOX) was prepared to add EGCG-dipalmitate. Amount of EGCG modification on liposomal membrane was

determined using DPPH assay. On P388 leukemia cells and M5076 ovarian sarcoma cells, cytotoxicity was evaluated by WST-8 assay and shown IC50. DOX uptake into tumor cells was evaluated in vitro. The concentration of doxorubicin into tumor cells was determined with a fluorescence spectrophotometer at an excitation wavelength of 500 nm and an emission wavelength of 550 nm.

Results and Discussion: Particle sizes of EL-DOX were 147 nm on average, zeta potential was -33.1 mV and encapsulated ratio of doxorubicin was 96.5 %. These data of sizes and zeta potentials were better for intravenous administration of liposomes. EGCG ratio on liposomal membrane (71.0 %) was enough to show its ability. In the study of doxorubicin uptake into tumor cells, EL-DOX group was increased amount of doxorubicin for 30 min. The doxorubicin level of EL-DOX was significantly higher compared with that of unmodified liposomal doxorubicin (p<0.05). At cytotoxicity, EL-DOX was stronger than unmodified liposomal doxorubicin. It was provided that IC50 of EL-DOX was also 125 times higher than EGCG solution which was reported to have been antitumor activity. Furthermore, co-incubation of EGCG solution and liposomal doxorubicin was not shown the enhancement effect both doxorubicin uptake into cells and the cytotoxicity. It was suggested that superior effect were shown in modification of EGCG around liposomal membrane, not mixture of EGCG and liposome. In conclusion, EL-DOX exhibited strong antitumor activity efficiently.

Citation Format: Ikumi Sugiyama, Kunihiro Kaihatsu, Nobuo Kato, Yasuyuki Sadzuka. Liposomal doxorubicin with modified EGCG increased antitumor activity by topical targeting efficiency into tumor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5408. doi:10.1158/1538-7445.AM2014-5408

Virus purification and enrichment by hydroxyapatite chromatography on a chip

The spread of infectious diseases has become a global health concern. In order to diagnose infectious diseases quickly and accurately, next-generation DNA sequencing techniques for genetic analysis of infectious viruses have been developed rapidly. However, it takes a very long time to pretreat clinical samples for genetic analysis using next-generation sequencers. We have therefore developed a microfluidic chromatography chip that can purify and enrich viruses in a sample using hydroxyapatite particles packed in a micro-column. We demonstrated the purification of virus from a mixture of virus and FBS protein, and enrichment of the virus using this novel microfluidic chip.

Synthesis and application of visible light sensitive azobenzene

Methods for regulating peptide conformation by non-harmful light stimuli can be useful for remotely controlling cellular functions in vitro. Here, we synthesized a series of p-heteroatom-substituted azobenzenes and studied their photoisomerization properties. The trans-isomer of p-sulfur-substituted azobenzene was effectively isomerized by visible light irradiation and the cis-isomer was thermally stable at physiological temperature. We developed a novel visible light sensitive amino acid (AZO), via p-sulfur-substituted azobenzene, and utilized it as a photosensitive modulator of the SV40 nuclear localization signal (NLS). The cellular uptake of the AZO-NLS conjugate was controlled by visible light irradiation. Our technology can be utilized for regulating not only the cellular uptake, but also the function of peptides within cells by non-harmful visible light irradiation.

Sequence-specific and visual identification of the influenza virus NS gene by azobenzene-tethered bis-peptide nucleic acid

To rapidly and specifically identify highly virulent influenza virus strains, we prepared an azobenzene-tethered hairpin-type peptide nucleic acid, bisPNA-AZO, which has a complementary sequence against a highly conserved genomic RNA sequence within the ribonucleoprotein complex of the 2009 pandemic influenza A virus, H1N1 subtype. bisPNA-AZO recognizes the conserved virus genome sequence in a sequence-specific manner. Immobilization of bisPNA-AZO on a plate allowed capture of the target virus gene and the generation of a visual colour signal.

Label-free single-particle imaging of the influenza virus by objective-type total internal reflection dark-field microscopy

Here we report label-free optical imaging of single particles of the influenza virus attached on a glass surface with a simple objective-type total internal reflection dark-field microscopy (TIRDFM). The capability of TIRDFM for the imaging of single viral particles was confirmed from fine correlation of the TIRDFM images with fluorescent immunostaining image and scanning electron microscopy image. The density of scattering spots in the TIRDFM images showed a good linearity against the virus concentration, giving the limit of detection as 1.2×10(4) plaque-forming units per milliliter. Our label-free optical imaging method does require neither elaborated sample preparation nor complex optical systems, offering a good platform for rapid and sensitive counting of viral particles.

Antibacterial and antifungal activities of new acylated derivatives of epigallocatechin gallate

(−)-Epigallocatechin-3-O-gallate (EGCG) has useful antiviral, antimicrobial, antitoxin, and antitumor properties. Previously, Mori et al. (2008) found that addition of long acyl chains (C16–18) to EGCG enhanced its anti-influenza virus activity up to 44-fold. The chemical stability of EGCG against oxidative degradation was also enhanced by acylation. We further evaluated the in vitro activity spectrum of the EGCG derivatives against a wide range of bacteria and fungi. A series of EGCG O-acyl derivatives were synthesized by lipase-catalyzed transesterification. These derivatives exhibited several-fold higher activities than EGCG, particularly against Gram-positive organisms. Antifungal MICs of the derivatives were also two to fourfold lower than those of EGCG. The activities of the EGCG derivatives against Gram-negative bacteria were not distinguishable from those of EGCG. Among the derivatives evaluated, MICs of dioctanoate and palmitate (C16) for 17 Staphylococcus aureus strains were 4–32 μg/ml, although MIC of EGCG for these 17 strains was ≥128 μg/ml. C16 demonstrated rapid bactericidal activity against methicillin-resistant S. aureus (MRSA) ATCC43300 at ≥16 μg/ml. The enhanced activity of C16 against S. aureus was supported by its increased membrane-permeabilizing activity determined by increased SYTOX Green uptake. The EGCG derivatives were exported in Escherichia coli using the efflux pump AcrAB–TolC. The tolC deletion mutant exhibited higher sensitivity to EGCG and the derivatives than wild-type. Addition of long alkyl chains to EGCG significantly enhanced its activities against several bacteria and fungi, particularly against S. aureus including MRSA. C16 might potentially become under specified circumstances an alternative or supplement to antibiotics and disinfectants in the future.

Regulation of duplex DNA strand displacement by visible light sensitive bis-peptide nucleic acid

A novel visible light sensitive azobenzene (AZO) was synthesized and introduced into bis-peptide nucleic acid (bis-PNA), which consists of two homopyrimidine PNA strands, as a linker. Visible light irradiation of the bis-PNA-AZO conjugate induced photoisomerization of the azobenzene moiety from trans to cis. The cis-form of bis-PNA-AZO displaced the complementary duplex DNA more efficiently than the trans-form.

Inhibition of influenza virus infection by targeting genome conserved region with non-natural nucleic acid

Two highly conserved 15 base sequences of influenza A virus genome were identified by CONSERV software, which can detect contiguous conserved sequences of biological sequences. Antiviral effect of phosphorothioate oligonucleotide that target these conserved sequences was evaluated by plaque formation assay and cell viability assay. Pre-treatment of cells with anti-PB2 (RNA polymerase subunit) reduced the size of plaques in a sequence dependent manner. Post-treatment of cells with anti-PB2 phosphorothioate oligonucleotide inhibited the virus-induced cytotoxicity.

Antioxidant and antiviral activities of silybin fatty acid conjugates

Two selective acylation methods for silybin esterification with long-chain fatty acids were developed, yielding a series of silybin 7-O- and 23-O-acyl-derivatives of varying acyl chain lengths. These compounds were tested for their antioxidant (inhibition of lipid peroxidation and DPPH-scavenging) and anti-influenza virus activities. The acyl chain length is an important prerequisite for both biological activities, as they improved with increasing length of the acyl moiety.

Inhibiting transcription of chromosomal DNA with antigene peptide nucleic acids

Synthetic molecules that recognize specific sequences within cellular DNA are potentially powerful tools for investigating chromosome structure and function. Here, we designed antigene peptide nucleic acids (agPNAs) to target the transcriptional start sites for the human progesterone receptor B (hPR-B) and A (hPR-A) isoforms at sequences predicted to be single-stranded within the open complex of chromosomal DNA. We found that the agPNAs were potent inhibitors of transcription, showing for the first time that synthetic molecules can recognize transcription start sites inside cells. Breast cancer cells treated with agPNAs showed marked changes in morphology and an unexpected relationship between the strictly regulated levels of hPR-B and hPR-A. We confirmed these phenotypes using siRNAs and antisense PNAs, demonstrating the power of combining antigene and antisense strategies for gene silencing. agPNAs provide a general approach for controlling transcription initiation and a distinct option for target validation and therapeutic development.

Intracellular uptake and inhibition of gene expression by PNAs and PNA-peptide conjugates

Peptide nucleic acids (PNAs) offer a distinct option for silencing gene expression in mammalian cells. However, the full value of PNAs has not been realized, and the rules governing the recognition of cellular targets by PNAs remain obscure. Here we examine the uptake of PNAs and PNA-peptide conjugates by immortal and primary human cells and compare peptide-mediated and DNA/lipid-mediated delivery strategies. We find that both peptide-mediated and lipid-mediated delivery strategies promote entry of PNA and PNA-peptide conjugates into cells. Confocal microscopy reveals a punctate distribution of PNA and PNA-peptide conjugates regardless of the delivery strategy used. Peptide D(AAKK)(4) and a peptide containing a nuclear localization sequence (NLS) promote the spontaneous delivery of antisense PNAs into cultured cells. The PNA-D(AAKK)(4) conjugate inhibits expression of human caveolin 1 (hCav-1) in both HeLa and primary endothelial cells. DNA/lipid-mediated delivery requires less PNA, while peptide-mediated delivery is simpler and is less toxic to primary cells. The ability of PNA-peptide conjugates to enter primary and immortal human cells and inhibit gene expression supports the use of PNAs as antisense agents for investigating the roles of proteins in cells. Both DNA/lipid-mediated and peptide-mediated delivery strategies are efficient, but the compartmentalized localization of PNAs suggests that improving the cellular distribution may lead to increased efficacy.

Recognition of chromosomal DNA by PNAs

The recognition of cellular nucleic acids by synthetic oligonucleotides is a versatile strategy for regulating biological processes. The vast majority of published studies have focused on antisense oligonucleotides that target mRNA, but it is also possible to design antigene oligonucleotides that are complementary to chromosomal DNA. Antigene oligomers could be used to inhibit the expression of any gene or analyze promoter structure and the mechanisms governing gene regulation. Other potential applications of antigene oligomers include activation of expression of chosen genes or the introduction of mutations to correct genetic disease. Peptide nucleic acid (PNA) is a nonionic DNA/RNA mimic that possesses outstanding potential for recognition of duplex DNA. Here we describe properties of PNAs and the challenges for their development as robust antigene agents.

Synthesis of peptide nucleic acid-peptide conjugates

Synthetic oligonucleotides are versatile tools for recognizing ribonucleic acid and deoxyribonucleic acid. This chapter describes methods for enhancing recognition by derivatizing oligonucleotides with either proteins or peptides.

Extending recognition by peptide nucleic acids (PNAs): binding to duplex DNA and inhibition of transcription by tail-clamp PNA-peptide conjugates

Peptide nucleic acids (PNAs) are a powerful tool for recognition of double-stranded DNA. Strand invasion is most efficient when pyrimidine PNAs are linked to form a bisPNA in which one strand binds by Watson-Crick base pairing while the other binds by Hoogsteen base pairing to the newly formed PNA-DNA duplex. Within many genes, however, polypyrimidine target sequences may not be located in optimal positions relative to transcription factor binding sites, and this deficiency may complicate attempts to identify potent antigene PNAs. To increase the versatility of strand invasion by PNAs, we have synthesized bisPNAs and bisPNA-peptide conjugates containing a mixed base extension of the Watson-Crick polypyrimidine strand. We find that these tail-clamp PNAs (TC-PNAs) bind duplex DNA and inhibit transcription. DNA recognition occurs with single-stranded or TC-bisPNAs and requires attachment of positively charged amino acids. Association rate constants, k(a), for binding to DNA by TC-PNAs are as high as 35000 M(-1) s(-1) and are usually only a fewfold lower than for analogous PNAs that lack mixed base extensions. The ability to bind duplex DNA is not always necessary for inhibition of transcription, possibly because PNAs can bind to accessible DNA within the transcription bubble created by RNA polymerase. These results, together with similar findings independently obtained by Nielsen and colleagues [Bentin, T., Larsen, H. J., and Nielsen, P. E. (2003) Biochemistry 42, 13987-13995], expand the range of sequences within duplex DNA that are accessible to PNAs and suggest that TC-PNA-peptide conjugates are good candidates for further testing as antigene agents.

Inhibition of transcription by bisPNA-peptide conjugates

Homopyrimidine bisPNAs have been reported to arrest transcription elongation by invading double-stranded DNA and forming a stable (PNA)2/DNA complex. We previously reported that attachment of a designed cationic peptide to the bisPNA enhances the efficiency of strand invasion. Here we investigate whether conjugation to cationic peptides can also improve inhibition of transcription. We observe that a conjugate between a bisPNA and a peptide containing eight lysines is a superior agent for inhibition of transcription, but that inhibition of transcription is reduced as pH and the concentration of magnesium are increased. Our studies provide useful characterization of bisPNAs as agents for inhibiting transcription.

Synthesis of non-natural DNA using DNA polymerase

Nonnatural nucleotide modified by glucose or galactose was synthesized to increase functional diversity of DNA library. These compounds were incorporated in a DNA double strand using Klenow Fragment as well as dTTP. These functional group could be ordered sequentially on a DNA double strand at intervals of few angstroms according to the designed template sequence within a few hours. This method must be useful to constructing nonnatural DNA library or designed supramolecular structures.

Enhanced strand invasion by peptide nucleic acid-peptide conjugates

Efficient and selective recognition of DNA by proteins is due to sequence-specific interactions with a target site and nonselective electrostatic interactions that promote the target's rapid location. If synthetic molecules could mimic these functions, they would render a wide range of chromosome sequences accessible to rationally designed probes. Here we describe conjugates between bispeptide nucleic acids (bisPNAs) designed to specifically recognize duplex DNA and peptides that have been designed to promote rapid sequence recognition. Peptide design was based on the surface of staphylococcal nuclease, a cationic DNA binding protein with low sequence selectivity. We observe that attachment of the designed peptide increases rates of strand invasion by 100-fold relative to unmodified bisPNA. The peptide can contain D-amino acids, increasing the likelihood that it will be stable in cell extract and inside cells. Binding of the conjugate containing the D-amino acid peptide occurred over a broad range of experimental conditions and was sensitive to a single mismatch. Strand invasion was efficient at neutral to basic pH, a wide range of temperatures (0-65 degrees C), and in the presence of up to 7 mM Mg(2+) and 100 mM Na(+) or K(+). Our data suggest that attachment of peptides that mimic cationic protein surfaces to PNAs can afford conjugates that mimic the rapid and selective binding that characterizes native DNA binding proteins. Rapid strand invasion over a wide range of experimental conditions should further expand the utility of strand invasion by PNAs.

Construction of nonnatural DNA library

Nonnatural DNA polymerase substrates which contain many kinds of modified functional groups are synthesized. The C-5 position of dUTP was modified by amino acid, saccharide. These compounds were incorporated on a DNA double strand using E. Coli DNA polymerase. This nonnatural DNA library contains a larger diversity than native DNA or RNA and has a higher chemical stability than RNA. This library will be useful for in vitro selection study, combinatorial chemistry, and the preparation of supramolecular structures.

Effects of chronic iron deficiency anemia on brain metabolism

The effects of chronic iron deficiency anemia on brain (cortex) metabolism were estimated by 31P-nuclear magnetic resonance spectroscopy and biochemical analyses in male Wistar rats. Iron deficiency anemia was induced by supplying diet containing either approximately 2 or approximately 6 ppm Fe. Control diet was supplemented with 100 ppm Fe as ferric citrate. After 8-9 weeks, blood hemoglobin levels were approximately 13, 5, and 3 g/100 ml in the 100 ppm, 6 ppm, and 2 ppm Fe group, respectively. The blood lactate levels at rest in these groups were approximately 3, 5, and 6 mM. The blood glucose concentration also tended to be elevated in iron-deficient rats. The high-energy phosphate contents in brain were not affected by iron deficiency. The activities of succinate dehydrogenase and cytochrome oxidase per unit protein in the 2 ppm Fe group were significantly less than in the 100 ppm Fe group, but those activities were not significantly affected by feeding diet with 6 ppm Fe. The activities of lactate dehydrogenase in iron-deficient group tended to be elevated but not significantly. The activities of non-iron containing mitochondrial enzymes, citrate synthase and beta-hydroxyacyl CoA dehydrogenase, were unchanged. It is suggested that the brain has a higher tolerance to iron deficiency than skeletal muscle in terms of the metabolic characteristics, although this may be associated with a lower level of neural activity.