Zhejiang mosquito virus 3

Taxonomy: Viruses; Riboviria; unclassified Riboviria; unclassified RNA viruses ShiM-2016

Average proteome isoelectric point is 9.28

Get precalculated fractions of proteins

Acidic
pI < 6.8
6.8-7.4
pI > 7.4
Basic
    
All



Virtual 2D-PAGE plot for 2 proteins (isoelectric point calculated using IPC2_protein)

Get csv file with sequences according to given criteria:
        -     Method 

     -  kDa    
                                                                                      

* You can choose from 21 different methods for calculating isoelectric point

Summary statistics related to proteome-wise predictions


    

Protein with the lowest isoelectric point:
>tr|A0A1L3KIH6|A0A1L3KIH6_9VIRU RNA-dependent RNA polymerase OS=Zhejiang mosquito virus 3 OX=1923779 PE=4 SV=1
MM1 pKa = 7.56SLPEE5 pKa = 4.41GVSGAIPPRR14 pKa = 11.84TPAGSHH20 pKa = 5.85EE21 pKa = 4.2PASAQVGRR29 pKa = 11.84PQPSPKK35 pKa = 10.42GLARR39 pKa = 11.84KK40 pKa = 7.42TNHH43 pKa = 5.01TQIPPTIVDD52 pKa = 3.8PKK54 pKa = 9.39SSPRR58 pKa = 11.84RR59 pKa = 11.84AHH61 pKa = 6.22PPKK64 pKa = 10.16KK65 pKa = 10.24ARR67 pKa = 11.84APGKK71 pKa = 9.48ATTKK75 pKa = 10.29PPASVQQKK83 pKa = 8.09QAQHH87 pKa = 5.34IWDD90 pKa = 4.33AFRR93 pKa = 11.84LSLWVLLPRR102 pKa = 11.84LQKK105 pKa = 10.59RR106 pKa = 11.84GLSTKK111 pKa = 10.4AVATIEE117 pKa = 4.54AIKK120 pKa = 10.6ALYY123 pKa = 9.32GWIGNSVACSGVEE136 pKa = 4.15FTAKK140 pKa = 9.37QVKK143 pKa = 9.77EE144 pKa = 3.73YY145 pKa = 11.33ANYY148 pKa = 9.83CRR150 pKa = 11.84ARR152 pKa = 11.84ALRR155 pKa = 11.84AQQCEE160 pKa = 4.17PPRR163 pKa = 11.84GFPIRR168 pKa = 11.84AFEE171 pKa = 3.99RR172 pKa = 11.84GYY174 pKa = 9.62IHH176 pKa = 7.62AMLACPGQGRR186 pKa = 11.84LHH188 pKa = 7.02LAQLARR194 pKa = 11.84VGRR197 pKa = 11.84AMPIGTTKK205 pKa = 10.54VAIASLRR212 pKa = 11.84KK213 pKa = 9.2HH214 pKa = 6.5RR215 pKa = 11.84EE216 pKa = 3.87VLSQPMDD223 pKa = 3.56TEE225 pKa = 4.03PALVEE230 pKa = 4.34KK231 pKa = 10.5LRR233 pKa = 11.84AWAEE237 pKa = 3.13IWTRR241 pKa = 11.84EE242 pKa = 3.8RR243 pKa = 11.84LGAGGRR249 pKa = 11.84TLTNPAAHH257 pKa = 7.09FSRR260 pKa = 11.84SASATVSALKK270 pKa = 10.56GGQLTEE276 pKa = 4.2LRR278 pKa = 11.84QLPAVAEE285 pKa = 4.55HH286 pKa = 6.35YY287 pKa = 11.31ALIQEE292 pKa = 4.54LLGDD296 pKa = 3.71QLDD299 pKa = 4.28PVTGEE304 pKa = 3.77PFEE307 pKa = 4.31WDD309 pKa = 4.09PYY311 pKa = 10.85TFDD314 pKa = 4.73ADD316 pKa = 3.42GGAIGLLTSASEE328 pKa = 4.23ADD330 pKa = 4.14DD331 pKa = 4.02LQILADD337 pKa = 3.86CALRR341 pKa = 11.84TATEE345 pKa = 3.98HH346 pKa = 6.92AADD349 pKa = 3.8NTPIPMTATVISEE362 pKa = 4.53LGMKK366 pKa = 10.1ARR368 pKa = 11.84VVTKK372 pKa = 9.07PPAWAVVAGDD382 pKa = 3.96ACRR385 pKa = 11.84KK386 pKa = 6.81TVWPLLEE393 pKa = 3.99GDD395 pKa = 3.89RR396 pKa = 11.84RR397 pKa = 11.84IDD399 pKa = 3.47LSGVRR404 pKa = 11.84PTAEE408 pKa = 3.82VLDD411 pKa = 4.38AFHH414 pKa = 7.74DD415 pKa = 4.06NLAHH419 pKa = 6.07SLVGARR425 pKa = 11.84STQFYY430 pKa = 10.74SADD433 pKa = 3.23LTAATDD439 pKa = 3.74LMPFDD444 pKa = 4.63VSRR447 pKa = 11.84AMWNGLCDD455 pKa = 4.0GLGATATAPLRR466 pKa = 11.84KK467 pKa = 9.69LGLYY471 pKa = 10.56LLGPVQVSYY480 pKa = 11.04PDD482 pKa = 4.74LSALPASSKK491 pKa = 10.81LYY493 pKa = 9.48VAGEE497 pKa = 4.05RR498 pKa = 11.84VEE500 pKa = 4.35CLSEE504 pKa = 4.13RR505 pKa = 11.84GCMMGLPVSWTVLNLYY521 pKa = 9.38NLAMADD527 pKa = 4.13LACTPEE533 pKa = 4.27GSPVLVNVAPAIARR547 pKa = 11.84GDD549 pKa = 3.93DD550 pKa = 3.6LVAAIPAEE558 pKa = 3.95EE559 pKa = 3.91ATRR562 pKa = 11.84YY563 pKa = 9.44EE564 pKa = 4.31DD565 pKa = 5.69LIAATGGEE573 pKa = 4.2ANRR576 pKa = 11.84LKK578 pKa = 10.73SFRR581 pKa = 11.84SADD584 pKa = 3.21AFVLAEE590 pKa = 3.95RR591 pKa = 11.84TFEE594 pKa = 4.14VGVLRR599 pKa = 11.84RR600 pKa = 11.84PNVEE604 pKa = 3.79LKK606 pKa = 10.11QRR608 pKa = 11.84GYY610 pKa = 7.25VTRR613 pKa = 11.84RR614 pKa = 11.84TYY616 pKa = 9.54RR617 pKa = 11.84TAPLLAQFDD626 pKa = 4.21SAEE629 pKa = 4.12LHH631 pKa = 6.53GGTGDD636 pKa = 3.44TRR638 pKa = 11.84RR639 pKa = 11.84LGDD642 pKa = 3.63APEE645 pKa = 4.13VVAIRR650 pKa = 11.84MACDD654 pKa = 3.28VPIRR658 pKa = 11.84SLLGGGPRR666 pKa = 11.84TVGANPVPDD675 pKa = 3.85YY676 pKa = 11.6VSIPPAAAACLAEE689 pKa = 4.31FEE691 pKa = 4.39GTRR694 pKa = 11.84LYY696 pKa = 10.93RR697 pKa = 11.84SVAEE701 pKa = 4.32GLMSVHH707 pKa = 6.84RR708 pKa = 11.84GLVADD713 pKa = 5.04LRR715 pKa = 11.84RR716 pKa = 11.84SAIPLFYY723 pKa = 10.24PRR725 pKa = 11.84EE726 pKa = 3.96LGGAGFPHH734 pKa = 7.16PKK736 pKa = 9.88GFAAAVASAGEE747 pKa = 4.34LGLKK751 pKa = 10.04RR752 pKa = 11.84AGLALTTAGHH762 pKa = 6.98KK763 pKa = 9.96AQQKK767 pKa = 10.19VGLLSCPWSPKK778 pKa = 8.69LTDD781 pKa = 3.32RR782 pKa = 11.84RR783 pKa = 11.84AKK785 pKa = 8.87EE786 pKa = 3.49ARR788 pKa = 11.84RR789 pKa = 11.84RR790 pKa = 11.84LIASDD795 pKa = 3.06QRR797 pKa = 11.84AWANSVLARR806 pKa = 11.84HH807 pKa = 6.69PDD809 pKa = 3.43LPRR812 pKa = 11.84GGSAWTNRR820 pKa = 11.84AAGEE824 pKa = 3.96LRR826 pKa = 11.84KK827 pKa = 9.92ALSVPSRR834 pKa = 11.84GFEE837 pKa = 4.05TVPRR841 pKa = 11.84GARR844 pKa = 11.84VAVALEE850 pKa = 3.95DD851 pKa = 3.55AVIRR855 pKa = 11.84EE856 pKa = 4.25VAAAAAWEE864 pKa = 4.17DD865 pKa = 3.68AFLGPGARR873 pKa = 11.84GWSGVPPPMQEE884 pKa = 3.84PSRR887 pKa = 11.84KK888 pKa = 8.92RR889 pKa = 11.84SARR892 pKa = 11.84QKK894 pKa = 10.16EE895 pKa = 4.53EE896 pKa = 4.0SLGMYY901 pKa = 9.55PSLGEE906 pKa = 3.6VARR909 pKa = 11.84RR910 pKa = 11.84LKK912 pKa = 9.94TIRR915 pKa = 11.84SQTQAARR922 pKa = 11.84FNRR925 pKa = 11.84TFLPKK930 pKa = 10.12RR931 pKa = 11.84AVQEE935 pKa = 3.67RR936 pKa = 11.84ARR938 pKa = 11.84FFDD941 pKa = 3.31RR942 pKa = 11.84LKK944 pKa = 10.88ALRR947 pKa = 11.84EE948 pKa = 4.18LEE950 pKa = 4.41TVLVPAQAAGARR962 pKa = 11.84LVVFDD967 pKa = 4.72PVTHH971 pKa = 6.48RR972 pKa = 11.84VSEE975 pKa = 4.38SAGEE979 pKa = 3.83IDD981 pKa = 3.83GGEE984 pKa = 3.89GRR986 pKa = 11.84MGFPLWRR993 pKa = 11.84HH994 pKa = 5.12TLQEE998 pKa = 4.24RR999 pKa = 11.84KK1000 pKa = 9.64GKK1002 pKa = 10.4RR1003 pKa = 11.84GAQGQEE1009 pKa = 3.55AAVPVPVATTRR1020 pKa = 11.84SGLSLGDD1027 pKa = 3.37VMTVRR1032 pKa = 11.84RR1033 pKa = 11.84LPRR1036 pKa = 11.84RR1037 pKa = 11.84PRR1039 pKa = 11.84GVRR1042 pKa = 11.84RR1043 pKa = 11.84LPNRR1047 pKa = 11.84SGAHH1051 pKa = 4.99SRR1053 pKa = 11.84NVRR1056 pKa = 3.24

Molecular weight:
113.82 kDa
Isoelectric point according different methods:






Protein with the highest isoelectric point:
>tr|A0A1L3KIH6|A0A1L3KIH6_9VIRU RNA-dependent RNA polymerase OS=Zhejiang mosquito virus 3 OX=1923779 PE=4 SV=1
MM1 pKa = 7.54GATSVGQPSNSPRR14 pKa = 11.84SPWQSSDD21 pKa = 2.89RR22 pKa = 11.84HH23 pKa = 5.88DD24 pKa = 3.7VPKK27 pKa = 11.2GEE29 pKa = 4.33TGPGRR34 pKa = 11.84SDD36 pKa = 3.39RR37 pKa = 11.84DD38 pKa = 3.16RR39 pKa = 11.84HH40 pKa = 6.18SRR42 pKa = 11.84LLTLGTPLPFPLLQRR57 pKa = 11.84MPPEE61 pKa = 4.83RR62 pKa = 11.84EE63 pKa = 3.96SHH65 pKa = 6.4SPFPTIDD72 pKa = 3.14LPGRR76 pKa = 11.84LRR78 pKa = 11.84NPMGDD83 pKa = 3.12GVEE86 pKa = 4.14NDD88 pKa = 3.28QTRR91 pKa = 11.84PRR93 pKa = 11.84SLCGDD98 pKa = 3.36QHH100 pKa = 7.33SLQLSEE106 pKa = 3.94GLKK109 pKa = 9.83TIEE112 pKa = 3.87EE113 pKa = 4.5AGSFLHH119 pKa = 7.15RR120 pKa = 11.84PFGQEE125 pKa = 3.41GAVEE129 pKa = 4.02PRR131 pKa = 11.84RR132 pKa = 11.84LSLRR136 pKa = 11.84PNRR139 pKa = 11.84LKK141 pKa = 10.78SPRR144 pKa = 11.84HH145 pKa = 4.33FPEE148 pKa = 4.4RR149 pKa = 11.84RR150 pKa = 11.84VHH152 pKa = 5.29PQRR155 pKa = 11.84LLLLAGRR162 pKa = 11.84ALARR166 pKa = 11.84RR167 pKa = 11.84LLHH170 pKa = 5.55WRR172 pKa = 11.84RR173 pKa = 11.84NSRR176 pKa = 11.84PASSTWAKK184 pKa = 10.46EE185 pKa = 3.98GVFPGGRR192 pKa = 11.84RR193 pKa = 11.84RR194 pKa = 11.84DD195 pKa = 3.77FADD198 pKa = 3.07HH199 pKa = 6.83GVFEE203 pKa = 5.13RR204 pKa = 11.84NGDD207 pKa = 3.48TGTAGHH213 pKa = 6.89RR214 pKa = 11.84LEE216 pKa = 4.31SPRR219 pKa = 11.84GNGQCLTQLPSCPVRR234 pKa = 11.84PCRR237 pKa = 11.84PSTRR241 pKa = 11.84EE242 pKa = 3.67VGVAGQDD249 pKa = 2.99RR250 pKa = 11.84VRR252 pKa = 11.84PRR254 pKa = 11.84SLIRR258 pKa = 11.84RR259 pKa = 11.84DD260 pKa = 3.16KK261 pKa = 10.58SAAGLFCSAVSEE273 pKa = 4.7FWGPWTRR280 pKa = 11.84KK281 pKa = 8.74EE282 pKa = 4.01SHH284 pKa = 6.95LLLCLVAGCRR294 pKa = 11.84QSQARR299 pKa = 11.84ALKK302 pKa = 10.68AKK304 pKa = 7.52LTCRR308 pKa = 11.84GDD310 pKa = 3.57CRR312 pKa = 11.84RR313 pKa = 11.84EE314 pKa = 3.65PLGVRR319 pKa = 11.84EE320 pKa = 3.96TRR322 pKa = 11.84APQFSGVEE330 pKa = 3.9QRR332 pKa = 11.84YY333 pKa = 9.52SRR335 pKa = 11.84TPEE338 pKa = 3.72VRR340 pKa = 11.84NKK342 pKa = 10.09TPVNGHH348 pKa = 5.36QSLGHH353 pKa = 5.92GAVEE357 pKa = 4.3PGSLEE362 pKa = 4.1LGQARR367 pKa = 11.84CSSRR371 pKa = 11.84RR372 pKa = 11.84YY373 pKa = 10.52GDD375 pKa = 4.07IIWNRR380 pKa = 11.84VGTDD384 pKa = 3.55GAGTPAKK391 pKa = 10.17EE392 pKa = 3.98GANRR396 pKa = 11.84NVAGHH401 pKa = 7.03ANGHH405 pKa = 5.29DD406 pKa = 3.51LRR408 pKa = 11.84RR409 pKa = 11.84ISEE412 pKa = 4.16AASVPSAAVEE422 pKa = 4.39FGAIEE427 pKa = 4.06LSKK430 pKa = 10.5QGRR433 pKa = 11.84RR434 pKa = 11.84TVSTTSYY441 pKa = 10.37IAPLLQLDD449 pKa = 3.43IRR451 pKa = 11.84TTKK454 pKa = 10.28HH455 pKa = 6.1SYY457 pKa = 11.21LEE459 pKa = 4.78GPLSQYY465 pKa = 10.88KK466 pKa = 10.34GIRR469 pKa = 11.84APEE472 pKa = 4.06ALEE475 pKa = 4.67AVGLPTGCSDD485 pKa = 3.76KK486 pKa = 11.16VFVPSRR492 pKa = 11.84LLGRR496 pKa = 11.84DD497 pKa = 2.97SRR499 pKa = 11.84HH500 pKa = 4.91EE501 pKa = 4.39VIASSYY507 pKa = 10.06RR508 pKa = 11.84GRR510 pKa = 11.84HH511 pKa = 4.29VDD513 pKa = 2.95QHH515 pKa = 6.05RR516 pKa = 11.84RR517 pKa = 11.84TLRR520 pKa = 11.84GTRR523 pKa = 11.84QVSHH527 pKa = 6.3CQVVQVEE534 pKa = 4.05HH535 pKa = 7.03RR536 pKa = 11.84PRR538 pKa = 11.84DD539 pKa = 3.55RR540 pKa = 11.84KK541 pKa = 10.12AHH543 pKa = 5.49HH544 pKa = 6.05TTPFAQALDD553 pKa = 3.64AFPRR557 pKa = 11.84NVQLGARR564 pKa = 11.84RR565 pKa = 11.84QGTQVRR571 pKa = 11.84VRR573 pKa = 11.84DD574 pKa = 3.74LDD576 pKa = 3.47RR577 pKa = 11.84AEE579 pKa = 4.06QVEE582 pKa = 4.42SEE584 pKa = 4.24LTQGGGRR591 pKa = 11.84SRR593 pKa = 11.84TQSVAEE599 pKa = 4.52TIPHH603 pKa = 6.29RR604 pKa = 11.84PAHH607 pKa = 5.03VEE609 pKa = 3.66RR610 pKa = 11.84HH611 pKa = 4.44EE612 pKa = 3.92VRR614 pKa = 11.84GGGKK618 pKa = 9.16VCAVEE623 pKa = 4.91LGGTSTNEE631 pKa = 3.62GVGQVVVEE639 pKa = 4.59GIEE642 pKa = 5.07DD643 pKa = 3.63LGSWADD649 pKa = 3.57SRR651 pKa = 11.84QVDD654 pKa = 3.54PTVPFEE660 pKa = 4.58KK661 pKa = 10.85GPDD664 pKa = 3.7GLPTGVSGHH673 pKa = 6.33HH674 pKa = 6.13CPGRR678 pKa = 11.84RR679 pKa = 11.84LRR681 pKa = 11.84HH682 pKa = 6.37DD683 pKa = 3.85PRR685 pKa = 11.84LHH687 pKa = 4.94TQLRR691 pKa = 11.84NDD693 pKa = 3.8CCGHH697 pKa = 6.32RR698 pKa = 11.84NRR700 pKa = 11.84GIVGRR705 pKa = 11.84MFGCSTEE712 pKa = 4.09SAVRR716 pKa = 11.84KK717 pKa = 9.55DD718 pKa = 3.47LQVVRR723 pKa = 11.84FGRR726 pKa = 11.84RR727 pKa = 11.84GQQAYY732 pKa = 9.18GAAVCIEE739 pKa = 4.2RR740 pKa = 11.84VRR742 pKa = 11.84VPLEE746 pKa = 3.12WLARR750 pKa = 11.84HH751 pKa = 5.29RR752 pKa = 11.84VEE754 pKa = 6.0LVAEE758 pKa = 4.02QLLDD762 pKa = 3.48EE763 pKa = 4.53RR764 pKa = 11.84VVFGHH769 pKa = 6.23RR770 pKa = 11.84WEE772 pKa = 4.12LTKK775 pKa = 10.67LRR777 pKa = 11.84KK778 pKa = 9.02LAALQRR784 pKa = 11.84AHH786 pKa = 7.42RR787 pKa = 11.84CRR789 pKa = 11.84SRR791 pKa = 11.84PGEE794 pKa = 4.07VCSGIRR800 pKa = 11.84KK801 pKa = 9.41SPAARR806 pKa = 11.84SQSLPGPDD814 pKa = 3.33FRR816 pKa = 11.84PRR818 pKa = 11.84SEE820 pKa = 4.22LLNEE824 pKa = 3.97RR825 pKa = 11.84GFRR828 pKa = 11.84VHH830 pKa = 6.85WLGQHH835 pKa = 6.65LPVLSKK841 pKa = 11.17ASDD844 pKa = 3.77GNFCRR849 pKa = 11.84ADD851 pKa = 3.63RR852 pKa = 11.84HH853 pKa = 6.28CPPDD857 pKa = 3.51SCEE860 pKa = 4.09LGEE863 pKa = 4.66VKK865 pKa = 9.06PTLPRR870 pKa = 11.84TGQHH874 pKa = 5.86SVDD877 pKa = 3.05ISTLEE882 pKa = 4.22GPNGEE887 pKa = 4.03AARR890 pKa = 11.84RR891 pKa = 11.84LTLLSPQRR899 pKa = 11.84AGTAIVGVLLDD910 pKa = 3.89LLGGKK915 pKa = 9.65FDD917 pKa = 3.5ATAGHH922 pKa = 6.19GVSYY926 pKa = 9.46PAIEE930 pKa = 4.09SLNRR934 pKa = 11.84FNSGYY939 pKa = 9.98CFRR942 pKa = 11.84RR943 pKa = 11.84QAALLKK949 pKa = 10.28AWQQYY954 pKa = 6.24PQRR957 pKa = 11.84KK958 pKa = 9.29AEE960 pKa = 4.04GVPDD964 pKa = 3.78VLRR967 pKa = 11.84LLLLNRR973 pKa = 11.84GRR975 pKa = 11.84GFGRR979 pKa = 11.84CLSRR983 pKa = 11.84SARR986 pKa = 11.84LLRR989 pKa = 11.84RR990 pKa = 11.84VRR992 pKa = 11.84STRR995 pKa = 11.84RR996 pKa = 11.84GLGVHH1001 pKa = 7.29DD1002 pKa = 4.54GGGDD1006 pKa = 3.51LGVVGLPGQPFRR1018 pKa = 11.84TGLRR1022 pKa = 11.84PTNLGTGGLVRR1033 pKa = 11.84ACRR1036 pKa = 11.84CPGRR1040 pKa = 11.84YY1041 pKa = 9.41GSAHH1045 pKa = 6.08SFRR1048 pKa = 11.84KK1049 pKa = 6.73THH1051 pKa = 5.23YY1052 pKa = 9.96RR1053 pKa = 11.84RR1054 pKa = 3.56

Molecular weight:
116.49 kDa
Isoelectric point according different methods:






Peptides (in silico digests for buttom-up proteomics)

Below you can find in silico digests of the whole proteome with Trypsin, Chymotrypsin, Trypsin+LysC, LysN, ArgC proteases suitable for different mass spec machines.

Try
ESI
ChTry
ESI
ArgC
ESI
LysN
ESI
TryLysC
ESI

Try
MALDI
ChTry
MALDI
ArgC
MALDI
LysN
MALDI
TryLysC
MALDI

Try
LTQ
ChTry
LTQ
ArgC
LTQ
LysN
LTQ
TryLysC
LTQ

Try
MSlow
ChTry
MSlow
ArgC
MSlow
LysN
MSlow
TryLysC
MSlow

Try
MShigh
ChTry
MShigh
ArgC
MShigh
LysN
MShigh
TryLysC
MShigh

General Statistics

Number of major isoforms

Number of additional isoforms

Number of all proteins

Number of amino acids

Min. Seq. Length

Max. Seq. Length

Avg. Seq. Length

Avg. Mol. Weight

2

0

2

2110

1054

1056

1055.0

115.15

Amino acid frequency

Ala

Cys

Asp

Glu

Phe

Gly

His

Ile

Lys

Leu

10.569 ± 2.541

1.896 ± 0.465

4.028 ± 0.036

5.498 ± 0.004

2.559 ± 0.068

9.668 ± 0.867

2.938 ± 0.73

2.275 ± 0.329

3.081 ± 0.362

9.953 ± 0.126

Met

Asn

Gln

Pro

Arg

Ser

Thr

Val

Trp

Tyr

0.995 ± 0.429

1.991 ± 0.2

7.251 ± 0.227

3.934 ± 0.433

11.848 ± 1.331

6.54 ± 0.534

5.213 ± 0.261

7.062 ± 0.028

1.28 ± 0.165

1.422 ± 0.198

Note: For amino acid frequency statistics the error has been estimated with the bootstraping (x100) at the protein level

Most of the basic statistics you can see at this page can be downloaded from this CSV file

For dipeptide frequency statistics click here
See this proteome in: uniprot_link
Proteome-pI is available under Creative Commons Attribution-NoDerivs license, for more details see here

Reference: Kozlowski LP. Proteome-pI 2.0: Proteome Isoelectric Point Database Update. Nucleic Acids Res. 2021, doi: 10.1093/nar/gkab944 Contact: Lukasz P. Kozlowski