Gher energy (364 keV) and relatively long half-life (8 d). In contrast, technetium-99 m (99mTc) is easy to obtain and has been widely used in departments of nuclear medicine all over the world. Moreover, its lower energy (140 keV) and shorter half-life (6 h) show greater clinical applications than 131I. Theoretically, we can radiolabel specific peptides with 99mTc by modifying the structure of the peptide,which will bind the advantages of 99mTc and small peptides together. This is the first report on the redesign, synthesis, biodistribution and tumor imaging of 99mTc-RRL, which may be 25033180 a new molecular probe targeting tumor angiogenesis.Fresh SnCl2 solution with different concentration of 0.1, 0.25, 0.5, 1, 2, 4, 6, 10 mg/mL were dissolved in 50 mM hydrochloric acid (HCl) respectively, and sodium tartrate were prepared just before use. The fresh 99mTc-pertechnetate generator eluant was obtained from a 99Mo-99mTc radionuclide generator (China Institute of Atom Energy). At room temperature, 7.4 MBq 99m TcO42 eluant (50 mL) was added in 50 mL fresh SnCl2 solution, 100 mL ammonium acetate buffer and 50 mL 1 mg/mL RRL. After 15?80 min, the labeled product was purified on a 0.7610 cm Sephadex G25 gel-filtration column with 0.05 M PB (pH 7.4) as eluate. Radioactivity and absorbance at 220 nm of all fractions were analyzed.Purification and Radiochemical Purity TestFor the quality control of labeling, a double-phase paper chromatography on Xinhua no. 1 filter paper was performed to measure labeling efficiency and radiochemical purity, with acetone and ethanol: ammonia: water (2:1:5) as mobile phase. A gel column chromatography method was used in purification of the peptide as follow. The radiolabeled RRL peptide was purified and separated from unbound reactants by chromatography on a Sephadex G25 gel-filtration column (0.7610 cm) at 20uC, which first eluted with 1 bovine serum albumin, and then eluted with phosphate-buffered saline (PBS, 0.05 M, pH 7.4). The intensity of the radioactivity of all the fractions was detected with radioactivity meters (National Institute of Metrology, Beijing, China), and the peptide purchase 11089-65-9 content of all fractions was measured at 220 nm using an ND-1000 spectrophotometer (Nanodrop Technologies, Wilmington, USA).Materials and Methods Ethics StatementThis study was carried out in PS-1145 site strict 23727046 accordance with the recommendations. All animal experiments were approved by Peking University Animal Studies Committee, according to the Guidelines for the Care and Use of Research Animals (Peking University, China) (Approval ID: J201138). The mice were maintained using a standard diet, bedding and environment, with free access to food and drinking water according to the guidelines. The mice were finally sacrificed by cervical dislocation under anesthesia to ease the suffering from fear and pain.In vitro StabilityA sample of 100 mL 99mTc-RRL at room temperature was used to observe the in vitro stability. And the in vitro stability was also determined by incubating 100 mL 99mTc-RRL with 900 mL of normal saline at room temperature and 900 mL of freshly collected serum at 37uC, respectively. The three aliquots were then analyzed at 0, 1, 2, 4 and 6 h by paper chromatography.Design and Synthesis of RRLNew probe was 
synthesized by solid-phase peptide synthesis (SPPS) method, purified by radio reversed-phase HPLC, and characterized by electrospray mass spectrometry. All chemicals used were of analytical grade and commercially available. The RRL pe.Gher energy (364 keV) and relatively long half-life (8 d). In contrast, technetium-99 m (99mTc) is easy to obtain and has been widely used in departments of nuclear medicine all over the world. Moreover, its lower energy (140 keV) and shorter half-life (6 h) show greater clinical applications than 131I. Theoretically, we can radiolabel specific peptides with 99mTc by modifying the structure of the peptide,which will bind the advantages of 99mTc and small peptides together. This is the first report on the redesign, synthesis, biodistribution and tumor imaging of 99mTc-RRL, which may be 25033180 a new molecular probe targeting tumor angiogenesis.Fresh SnCl2 solution with different concentration of 0.1, 0.25, 0.5, 1, 2, 4, 6, 10 mg/mL were dissolved in 50 mM hydrochloric acid (HCl) respectively, and sodium tartrate were prepared just before use. The fresh 99mTc-pertechnetate generator eluant was obtained from a 99Mo-99mTc radionuclide generator (China Institute of Atom Energy). At room temperature, 7.4 MBq 99m TcO42 eluant (50 mL) was added in 50 mL fresh SnCl2 solution, 100 mL ammonium acetate buffer and 50 mL 1 mg/mL RRL. After 15?80 min, the labeled product was purified on a 0.7610 cm Sephadex G25 gel-filtration column with 0.05 M PB (pH 7.4) as eluate. Radioactivity and absorbance at 220 nm of all fractions were analyzed.Purification and Radiochemical Purity TestFor the quality control of labeling, a double-phase paper chromatography on Xinhua no. 1 filter paper was performed to measure labeling efficiency and radiochemical purity, with acetone and ethanol: ammonia: water (2:1:5) as mobile phase. A gel column chromatography method was used in purification of the peptide as follow. The radiolabeled RRL peptide was purified and separated from unbound reactants by chromatography on a Sephadex G25 gel-filtration column (0.7610 cm) at 20uC, which first eluted with 1 bovine serum albumin, and then eluted with phosphate-buffered saline (PBS, 
0.05 M, pH 7.4). The intensity of the radioactivity of all the fractions was detected with radioactivity meters (National Institute of Metrology, Beijing, China), and the peptide content of all fractions was measured at 220 nm using an ND-1000 spectrophotometer (Nanodrop Technologies, Wilmington, USA).Materials and Methods Ethics StatementThis study was carried out in strict 23727046 accordance with the recommendations. All animal experiments were approved by Peking University Animal Studies Committee, according to the Guidelines for the Care and Use of Research Animals (Peking University, China) (Approval ID: J201138). The mice were maintained using a standard diet, bedding and environment, with free access to food and drinking water according to the guidelines. The mice were finally sacrificed by cervical dislocation under anesthesia to ease the suffering from fear and pain.In vitro StabilityA sample of 100 mL 99mTc-RRL at room temperature was used to observe the in vitro stability. And the in vitro stability was also determined by incubating 100 mL 99mTc-RRL with 900 mL of normal saline at room temperature and 900 mL of freshly collected serum at 37uC, respectively. The three aliquots were then analyzed at 0, 1, 2, 4 and 6 h by paper chromatography.Design and Synthesis of RRLNew probe was synthesized by solid-phase peptide synthesis (SPPS) method, purified by radio reversed-phase HPLC, and characterized by electrospray mass spectrometry. All chemicals used were of analytical grade and commercially available. The RRL pe.