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jianchaoyv金蟲(chóng) (小有名氣)
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【討論】關(guān)于不同z值處的水能形成氫鍵數(shù)的腳本討論 已有3人參與
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《轉(zhuǎn)載》 氫鍵判據(jù)用的是常用的35度3.5埃的幾何判據(jù),當(dāng)然也可以直接在腳本里改。計(jì)算方法是,只要有水分子有一個(gè)原子在某一層里,則這個(gè)水分子就認(rèn)為屬于這一層的水。對(duì)于每一幀,計(jì)算屬于每一層的水selin與其它物質(zhì)selbig之間的氫鍵數(shù),氫鍵包括了這一層中的水作為氫鍵受體和供體兩種情況,其數(shù)目分別為代碼中的變量a和b。并且加上這一層水內(nèi)部之間的氫鍵數(shù)(變量c)的2倍。a+b+2c除以這一層的水?dāng)?shù),作為這一幀這一層的每個(gè)水的平均氫鍵數(shù)。腳本中循環(huán)軌跡中的每一幀,最終得到這一層平均氫鍵數(shù)。nonum變量記錄有多少幀在所設(shè)定的范圍里沒(méi)有水,這些幀不計(jì)算。#后面那行用于調(diào)試目的,要考察每幀結(jié)果就去掉開(kāi)頭的#。 首先運(yùn)行下面的腳本,來(lái)加載實(shí)現(xiàn)這個(gè)功能的子程序 proc numhbavg {sel fps1 fps2} { set selin [atomselect top $sel] set selbig [atomselect top "same resid as exwithin 3.5 of $sel"] set k 0.0 set nonum 0 for {set i $fps1} {$i<=$fps2} {incr i} { $selin frame $i $selin update $selbig frame $i $selbig update if {[$selin num]!=0} { set a [llength [lindex [measure hbonds 3.5 35 $selbig $selin] 0]] #measure hbonds 3.5 35 $selbig $selin這個(gè)命令返回什么樣的值?怎么又先用了lindex、llength命令? set b [llength [lindex [measure hbonds 3.5 35 $selin $selbig] 0]] #這句跟上句的區(qū)別? set c [llength [lindex [measure hbonds 3.5 35 $selin] 0]] #這句為何只有一個(gè)$selin?一般都是像上2句那樣有2個(gè)$selin $selbig或$selbig $selin? set k [expr $k+($a+$b+2*$c)*3.0/[$selin num]] #puts "fps:$i $a+$b+[expr 2*$c] num_water:[expr [$selin num]/3.0] avg:[expr $k+($a+$b+2*$c)*3.0/[$selin num]]" } else {incr nonum} } if {[expr $fps2-$fps1+1]==$nonum} {return "no result"} return [expr $k/[expr $fps2-$fps1+1-$nonum]] } 然后下面的循環(huán)會(huì)調(diào)用這個(gè)子程序來(lái)輸出每一層的平均氫鍵數(shù),這里假設(shè)要計(jì)算z=4.0~5.6埃的數(shù)據(jù),間隔為0.1埃,且限定20 set k [expr $i*0.1] set now [numhbavg "same resid as resname SOL and x<40 and x>20 and y<40 and y>20 and z<[expr $k+0.1] and z>=$k" 100 150] puts [format "%4.2f %4.2f %5.3f" $k [expr $k+0.1] $now] } 我這里隨便算一個(gè)主要由水構(gòu)成的普通的體系,水形成的氫鍵數(shù)大概在3.1左右,標(biāo)準(zhǔn)放寬到4.0埃,40度,則可形成氫鍵數(shù)約為3.6。在冰中由于結(jié)構(gòu)十分有序,可形成4個(gè)氫鍵,在液態(tài)情況下分子的動(dòng)能必然造成氫鍵的破壞,所以結(jié)果是很合理的。 幀數(shù)范圍越大、xy平面越大計(jì)算越慢,這個(gè)腳本計(jì)算速度比較慢,不要一下將范圍設(shè)得太大。 輸出結(jié)果如下,前兩列代表統(tǒng)計(jì)的z值范圍,第三列是水的平均氫鍵數(shù) 4.00 4.10 3.015 4.10 4.20 3.161 4.20 4.30 3.201 4.30 4.40 3.159 4.40 4.50 3.237 4.50 4.60 3.130 4.60 4.70 3.201 4.70 4.80 3.338 4.80 4.90 3.201 4.90 5.00 3.041 5.00 5.10 3.122 5.10 5.20 3.182 5.20 5.30 3.160 5.30 5.40 3.309 5.40 5.50 3.189 5.50 5.60 3.327 請(qǐng)各位指點(diǎn)一下,我把自己看不懂的寫(xiě)在上面了,不過(guò)可以對(duì)程序解釋的越詳細(xì)越好,更便于本人的正確理解。∑诖魑桓呤种更c(diǎn)!尤其是bay__gulf ! 另:氫鍵幾何判據(jù)中角度到底指的哪個(gè)?vmd中的measure hbonds 的命令中的角度指的是:“the angle formed by the donor, hydrogen, and acceptor must be less than angle from 180 degrees. “ 而我看到的文獻(xiàn)Phys. Chem. Chem. Phys. , 2004, 6, 829–835 中氫鍵幾何判據(jù):“The bond angle a between the O–O direction and the molecular O–H direction of the donor, where H is the hydrogen which forms the bond, is lower than a threshold angle aC ”這兩個(gè)好像不一致。 [ Last edited by jianchaoyv on 2010-6-29 at 10:54 ] |
木蟲(chóng) (著名寫(xiě)手)
未來(lái)國(guó)家凍涼

金蟲(chóng) (著名寫(xiě)手)
劉蘇州
金蟲(chóng) (小有名氣)
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程序來(lái)源于http://hi.baidu.com/sobereva/blo ... 595ef7fc037fbf.html 麻煩最上面程序中還有問(wèn)題請(qǐng)教!請(qǐng)給解釋一下 另外,bay__gulf 那個(gè)vmd圖畫(huà)的與vmd的ug中描述好像不符吧?? [ Last edited by jianchaoyv on 2010-6-29 at 14:43 ] |
金蟲(chóng) (著名寫(xiě)手)
劉蘇州
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hbonds cutoff angle selection1 [selection2]: Find all hydrogen bonds in the given selection(s), using simple geometric criteria. Donor and acceptor must be within the cutoff distance, and the angle formed by the donor, hydrogen, and acceptor must be less than angle from 180 degrees. Only non-hydrogen atoms are considered in either selection. If both selection1 and selection2 are given, the selection1 is considered the donor and selection2 is considered the acceptor. If only one selection is given, all non-hydrogen atoms in the selection are considered as both donors and acceptors. The two selections must be from the same molecule. The function returns three lists; each element in each list corresponds to one hydrogen bond. The first list contains the indices of the donors, the second contains the indices of the acceptors, and the third contains the index of the hydrogen atom in the hydrogen bond. Known Issue: The output of hbonds cannot be considered 100% accurate if the donor and acceptor selection share a common set of atoms. ============= $selbig $selin這個(gè)命令返回什么樣的值?怎么又先用了lindex、llength命令? 請(qǐng)?jiān)谏厦嬲掖鸢?br /> #這句跟上句的區(qū)別? 逐字比對(duì) 這句為何只有一個(gè)$selin?一般都是像上2句那樣有2個(gè)$selin $selbig或$selbig $selin? 請(qǐng)?jiān)谏厦嬲掖鸢?br /> 氫鍵幾何判據(jù)中角度到底指的哪個(gè)? 請(qǐng)?jiān)谏厦嬲掖鸢?br /> vmd 的ug 較長(zhǎng), 全部打印不現(xiàn)實(shí) 但8,10,11三章一定要打印下來(lái)仔仔細(xì)細(xì)看 |
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