いろんな方法をためした結果以下の方法が、一番再現よく、収量もよくお気に入りです。 
dsDNAをPCRをラベルして、いらない方のStrand(末端がリン酸化されたstrand)をNucleaseで特異的に分解する方法です。 
Good luck 
Preparation of single strand long DNA probe 
01. Phosphorylation of oligonucleotide  
a. 5' phosphorylation 
Mix following mixture  
2 ul of 100 uM oligonucleotide 
4 ul of 10 x Kinase Buffer A 
4 ul of 10 mM ATP 
2 ul of 10 U/ul T4 PNK (Nippon Gene) 
28 ul of H2O 
--------------------------------------- 
total 40 ul 
Incubate it at 37C for 60 min. 
add 2 ul of 100 mM DTT (final 5 mM) 
Incubate it at 37C for 60 min. 
 
b. Purify oligonucleotide with MicroSpin G-25. 
c. EtOH precipitation 
d. dissolve the precipitant with 20 ul of H2O (final 10 uM). 
 
02. Probe Amplification by PCR  
 a. direct labeling by PCR     
      2.5 ul of 10 x ExTaq buffer 
      1 ul of 2 mM dNTP mixture ** (2 mM dA, dG, dCTP and 1 mM dTTP) 
      1 ul of 1 mM Biotin-16-dUTP (Roche) 
2 ul of 10 uM 5' P-primer 
2 ul of 10 uM ICON primer 
      0.5 ul of ExTaq 
         1 ul of template DNA 
       15 ul of H20 
      ---------------------------------------- 
total 25 ul / 40 cycle 
yield:   ~ 1.5 ug / 25 ul reaction 
incorporation efficiency : Biotin-14-dCTP (invitrogen)  << Biotin-16-dUTP (roche) 
 
b. Purify with Qiaquick PCR purification kit. Elute with 30 ul of EB 
c. Quantify the amount of DNA. | 
      
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